I want to thank all of you for the advice. I was thinking hobie 18 or nacra 5.7 - but as was mentioned on another post - you often get what is available... I could not find hobie or nacra in good condition/price within driving distance.

The Supertcat 17 was appealing to me, buoyancy and clean tramp - and I found one which the owner assured me was in great condition 5 hours from here - so off I went. But when I got there, there was a hole in exposed fiberglass at the back of one transom, and the other transom had cracks at the joint between transom and hull - and it look deep and the transom was soft/springy. The sail had holes 2-4 inches long over every batten where the sail hits the stay (when letting it out). Funny what people will describe as "good condition". Oh well - my son and I had a good road trip at least out of it!

So in the end, I found a 1982 prindle 16 that was in extremely good conditions: no soft spots, no dings anywhere. a set of racing white sails in very good contition + the original main sail in almost new condition (appeared to have been stored when the boat was bought and almost never used). I also got beach wheels and a good condition trailer. Trampoline was 4 years old - but boat had been stored for two years (owner had moved on to larger boat).

I know 18 foot was more recommended - but I could not find one. Prindle 16 increased buoyancy over hobie should allow me to get at least two kids out at the time. In the end we reasoned this way: start with something in good condition and affordable - and if the family likes it - move to larger - and more money (maybe hobie 21 or supercat 20).

Again thanks to all for your info. going to lake Ontario tomorrow to try it out.