staying at venture out in pcb with kids ages 8-10-13 any suggestions?

You can always go to pier park lot's of stuff to do there. Or go to Alvin's Island Magic Mountain, they have an arcade downstairs.
Rocket Lanes....they have arcade games, roller skating, bowling, and pizza parlor all under the same roof.
St Andrews State Park is just a short walk from Venture Out.
All good suggestions. Miracle Strip at Pier Park would be great. Everyone loves Gulf World Marine Park. St. Andrews State Park and Camp Helen State Park are both amazing parks with beautiful Gulf views. You could take a ride on the St. Andrew Bay Ferry, walk the M.B. Miller Pier or Russell-Fields Pier and go to WonderWorks. Of course you'll want to spend some time on the beach :)
Try the jet ski tour or boat tour to visit shell island. Or rent a pontoon boat to take to shell island. Pirates cove is next to venture out they have a great company there Sunshine Water Sports PC. By far the best thing to do in PCB, FL is visit shell island.
When my kids were that age their favorite thing to do was to go to Shipwreck Island water park.
We always did that one day to get away from the beach. The chicken tenders and the onion rings were good too, but I haven't been in awhile. We stayed the entire day to get our moneys worth.
All of the other days we went to the beach. I carried many things down there for them to do. Boogie boards or floats are good. Shovels and buckets for making sand castles. And of course plenty of snacks and drinks. It is easier to rent beach chairs and umbrellas, but you can buy inexpensive ones too ahead of time. At some point everyone will need some shade. My boys always looked forward to the afternoon when we went to our swimming pool.
There are many places to play miniature golf and most kids like that. And there are race car tracks that my boys liked. We always went souvenir shopping and everyone picked out their own t-shirt.
They will have lots of fun!
I would say Wonder Works would be a blast as well as one of many go-carts or jet ski rentals! Plenty to do in PCB!
DEFINITELY go to Shipwreck Water Park. We go every year. Get there before the gates open and there when they're shutting it down section by section. Admitedly it's expensive but when you're there all day it's worth it. The food is also expensive but it's good and they give you very large portions. 2 people could easily share a cheeseburger and fries.
Also agree about the arcades, go carts and all the putt putt courses too.
I personally was not impressed w/Shell Island. I've been twice and found more shells in front of my condo than there. This may have changed but last time I was there, there weren't any restroom facilities and for little girls that's pretty tough. When we went, oh my.....10 yrs ago??...we had a bad storm to blow up and of course every one is running for the boats to get off the island. Was NOT a pleasant experience---I have a problem w/lightening near water, rain that feels like needless hitting into your sunburned skin...no shelter......yea, not a good thing! LOL! :)
PCB is an AWESOME family destination. No matter what you do, you'll have a BLAST!
Karen