If you want to do JUST Theme Parks and Disney, Walt Disney World is a large Resort area where many folks don't even leave Disney property during their visit.
On the other hand, coming to Southern California, you are coming to the Birthplace of Theme Parks, and for many brands. The parks are built in the main part of cities, so you have a lot more choices, not just many Theme Parks, but a chance to check out the beaches, and other tourist attractions, such as natural parks, museums, etc.
In Southern California you can base yourself in Anaheim, and have good access to the two Disney run parks at the Disneyland Resort (DIsneyland was the first park and opened on July 18th, 1955), Knott's Berry Farm, America's 1st Theme Park, SeaWorld San Diego (the 1st), LEGOLAND (USA's 1st location), Universal Studios (the original) and Six Flags Magic Mountain.
So it depends, but due to the variety, and usually better weather (less humid in the summer, and less rain in the winter), I would look at Anaheim.
A poster on this forum has made statements to the effect that cities are cities and museums are museums and zoos are zoos so perhaps theme parks are theme parks using that same logic -- I personally don't agree with the first premise and therefore with the secondary premise
On the other hand Forbes Travler magazine released some numbers that are often quoted by that poster and the most popular attraction is Disneyworld so if you want to go by just pure numbers, then Disneyworld is the place to go.
The Orlando Kissimmee area is theme park heaven and most just stay there for a few weeks and go to all the parks. Southern California is huge. But if you want to just to Disneyland which is magical and amazing then you can stay in Anaheim and enjoy that park.
But there is a lot more to see in SoCal and if you are interested in LA and Hollywood and San Diego then most posters would advise you to split up your time and not waste an hour or two in traffic each way to get to the other areas.
It sounds like the rest of your trip is centered here in the west.
I am not clear as to how much time you have planned out already??
As mentioned above, folks go to Disneyworld to stay inside the resort. Florida is a tropical climate so they also will find hotter more humid weather and often lower hotel prices since real estate there is also cheaper.
In California the amusement parks are more spread out. We have a more temperate Mediterranean climate and there are more other things to see/do than theme parks.
I would encourage you to have your children get on their computers to do some research and allow them some input into this decision.
I wouldn't do both places on 2 coasts for this first trip.
They are too young to have this be a "once in a lifetime" trip.
To me, Theme Park Heaven is Southern California, more history, many more Roller Coasters in California (Yes, plenty of Roller Coasters in Northern California), but even just the Southern California area has many more than Florida.
Yes, both areas have Outlet Malls and family Dinner Theaters, but Southern California has more things than just that. Things like a National Forest, State and Regional parks (aka Outdoors/wildlife).
Good Public transit for the most part, a lot more choices in Hotels and other accommodations.
To many, California is the place to enjoy Theme Parks and Roller Coasters instead of Florida.
I can appreciate all of the above posts - and agree - BUT if you are wanting a Disney experience then Disney World is hands down much much MORE than Disneyland. Both are nice, but Disneyland has enough for only a few days whereas Disneyworld can fill a two week vacation and you still won't have done it all.
I once read that WDW is the size of San Fran. I believe it! It really is its own world (own fire dept, etc).
Imo, if you only want to carve 2-3 days out for Disney, then California will be fine; but if you have a week to spend on JUST Disney, go to Florida. If people ask, I always say Disneyland is a great first time Disney experience and Disneyworld after that - but if you can only go once - then Disneyworld.
I think the above posters have summarized it well. Disney has four full parks in Florida plus an entire resort area, plus other companies have theme parks nearby (such as Universal Orlando and Sea World Orlando, so you could easily spend two weeks or more there doing nothing but theme parks and never really leave the immediate vicinity of Disney.
Here in the Southern California area, there are two Disney theme parks which are right next to each other (Disneyland and Disney's California Adventure) but other non-Disneytheme parks are further away. Knott's Berry Farm is the closest (about 7 miles), then there's Universal Studios (about 35 miles from Disney), Magic Mountain (about 60 miles from Disney and rollercoaster paradise), Legoland in Carlsbad (geared towards kids, about 65 miles from Disney) and then in San Diego there's Sea World (about 90 miles from Disney). There's also several waterparks, mostly near the other theme parks but these are only open seasonally in spring and summer (note that our seasons are opposite from yours in Australia - when its winter there its summer here, etc.)
And don't forget the Zoos, the San Diego Zoo and San Diego Zoo Safari Park, plus the Los Angeles Zoo and the Santa Ana Zoo.
And then the Kids Friendly Science Museums, you have the Discovery Science Center in Santa Ana near Disneyland, the Reuben Fleet Science Center in San Diego (Balboa Park near the Zoo), and the California Science Center in LA, the home of one one of the Space Shuttles.
Plus the USS Midway Aircraft Carrier Museum and nearby Maritime Museum in San Diego.
The Aquarium of the Pacific in Long Beach, along with the Queen Mary,
Tar Pits, Automotive Museums, and much more.
So do you want the "Disney" experence, in Orlando, they will pick you up at the airport, and then pretty much you are on property 24/7 and use their transit systems to get between the parks and other options.
If you want more variety, not just in the types of Theme Parks, but all the other options, you can rely on Public Transit and Mass Transit, such as Tour Companies to get around if you don't want to drive.
Both options are good, it depends on what your family wants.
And let me also talk about Northern California and the San Francisco Bay area.
Yes, you have the classic Tourist attractions in the city, such as Alcatraz, Fisherman's Wharf, the Golden Gate Bridge and the Cable Cars.
But if you get outside the city, you have Six Flags Discovery Kingdom, a three-in-one park, a ride park, a marine park and a zoo all for one admission charge.
California's Great America, and thanks to the fact the the San Francisco 49'ers is building a stadium in its parking lot, they are building a new Wooden Roller Coaster Gold Striker opening later this year. This is a combo park, so a ride park and water park with the same admission fee.
Gilroy Garden is a Family/Horticultural Theme Park.
Santa Cruz Beach Boardwalk is a classic with a couple of great Roller Coasters and other attractions.
A few stand alone Water Parks, such as Raging Waters are in the area.
And then classic Tourist attractions such as the Mystery Spot and the Winchester Mystery House.
Lots of great popular tourist spots that families love to attend....
Personally - I don't think the two are comparable. Disneyland is the original ... California Adventure is added. I love them both, but they are an island in the middle of what became suburbia. (When I was a kid, it was orange groves!)
Orlando - massive area - an enclave - its own county. Golf courses and water parks and 4 theme parks. Several hotels and other activities. DH enjoyed the fishing! We never left Disney property.
So they are not the same. I can say without a doubt that I prefer the weather in Southern California. Hands down.
Also - California has so much more to offer than Disneyland - so you can easily build a great vacation around it. A vacation that offers more than Disney.
Let me say, to most Tourists, when they say LA, they mean the Greater Los Angeles Area, aka Southland, basically all of Southern California besides San Diego County... (an official Government term describing the area)
And there are plenty of Golf Courses in the Orange County area near Disneyland for those who like to play golf...