It may be the smart thing to start with a 22 unless you have so many family members a 25 is dictated. I would definately consider all the ways you'll use the boat or contemplate using it. When I purchased the C-Dory I never thought about camping in the mountains with it, but one of the most fun things I've done is using the thing as an RV throughout the Rockies. Some of the areas I've gotten into I simply couldn't in the 25 (I've had bigger boats than 25).
So you might want to test the waters with a 22 for a few years and see how it goes. Some have moved up in size, and some of us moved down and found less was more. Works both ways (both are great boats).