First off, all beach cats can capsize - there's no way around that.

Most of the 20 foot (6.0 meter) boats out there would not be suitable as a first cat, especially for someone planning to take a small child out. The NACRA 6.0, Mystere 6.0, Hobie 20 etc are all powerful race boats. Granted, it sounds like you're a fairly experienced sailor, but beach cats are different from monos and there will be a learning curve. It's probably best to look for a boat that will essentially be suitble for you to single hand. At 5 years old, your son isn't likely to provide much ballast or crew support.

A Hobie 17 Sport would probably be perfect. A Hobie 16 or 18 might also fit the bill (the 18 has plenty of flotation in the bows). I don't have enough familiarity with the other brands, but basically look for something that you can easily single hand.

sm