You bet Bill. I hear ya on the kids. In my experience, the little ones' biggest problem is in flipping the board up. Once the board is on the surface the kids litterally POP out of the water.
I like to use the Trick Boardz Velocity - Medium for teaching kids. The board is neutrally bouyant and so it allows them to get the forward rail out of the water with little trouble. I haven't priced them lately, but they have always been the least expensive board on the market. Larry and David Mann are great to work with.
Thinking about it, Trick Boardz has an innovative board selector and you might be able to get a single board for the entire family. Although, more than likely Dad will need his own board and Mom and the kids can ride a smaller one.
Personally, I prefer to teach adults on a bigger board. We had really good results with a 5'6" hyperlite broadcast. Although, you'll probably want a more responsive board after the first season. The WP Comp X 5-Oh is a good low cost alternative also. Bigger is usually better, for adults, when first starting out. If you want to cut your teeth on a cheap and easy to find board, the 5'6" Broadcast would be an ok first board.