When I travel with the kids I usually use VRBO, but the responce rate in San Francisco was terrible. This was the first time I used the TripAdvisor vacation rentals. Everyone I contacted on TripAdvisor responded right back. The Canterbury was the best deal I could find. The hotel room was spacious and close enough to Powell and Union Square so you could use all of the MUNI to get all over the city.
Stop by the Walgreens two blocks down on Powell and Sutter to buy you MUNI pass for your stay. It works on all of the mass transit but the BART. Avoid using the Powell cable car to get around it is slow and crazily over crowded. If you do want to ride it, avoid trying to catch it a Powell and Market unless you have a couple of hours to kill, just catch it on Powell and Sutter.
The front desk was extremely helpful and provided guides, recommendations to nearby reasonably priced restaurants, even some with coupons. They don't provide daily maid service, but we were there 5 nights and it was not a problem. The gym is adequately equipped for a workout: free weights, CYBEX treadmill, ellipticals, and weight machines.
The nice thing is it is just as convenient to downtown as the hotels on Powell, just 2 1/2 blocks from the Marriott or Sir Francis Drake, at about 1/2 the price for a room that comfortably sleeps 4 with a small kitchenette. The room was nicely appointed and up to date. It is technically in Nob Hill, but it is two blocks north of the Tenderloin. The neighborhood is extremely safe, however, if you go even one block south to Post and west towards Van Ness you will run into some ladies/men of the evening after the sun goes down. I would recommend it for both business and families.