First,
Realize that the correct number of boats is "one more". This is an important first step in any true boat lovers awareness of the afliction.
The reason that this is important is that you and your family will need more than one boat. You may start out with a Hobie 16, a Getaway, or a Hobie 20. It really does not matter, because your boys will love it and will sooner or later monopolize the boat. Your next boat can be a Hobie pedal kayak to chase out to the boys on the capsized boat, or one of the boats you think is missing in the mix.
I tell you this because our family started with a cat when I was eight. Since then we have owned aVenture 15, Prindle 16, three different Aqua Cats (Waves are better, but you get the point), a laser, two pedal kayaks, an inflatable with outboard, a catalina 27, a sabot, a Hobie 20, a Prindle 15, a Boston Whaler 14, and an aluminum 15' with outboard, and various windsurfing riggs from cruisers to racers to wave sailing machines. The 16 was given away three times before it didn't come back, the Aqua cats were all sold or given away, the Whaler stolen, the laser sold, the Prindle 15 sold. The next boat on the list is a Wave for the kids this summer, and then Maybe another race boat for me.
Sail on what you intend to buy first. I have watched too many people buy over there comfort level. You may sail with everyone occasionally, but usually it will only be two or three on the boat. That is why the second boat is only a matter of time.
