I second the idea of looking at what the nearest yacht club uses for junior sailing lessons/racing and looking for one of those, with his requirement of a pointy nose of course. Or a laser if he's ready for that.
But it sounds like you are going to build, so this reminded me that I have a complete set up for an El Toro:
Mast, boom,
rigging, nice mylar
racing sail, mainsheet, dagger board,
rudder and tiller. The El Toro is 8' but has a square bow. However, you could probably use this stuff for most small boats you build with minimal modifications.
Unfortunately a storm blew the
hull, (which was tied down with too light of line), off my
dock. So this stuff has been sitting forgotten in my crawl space for a couple decades.
Shipping would be an effort; maybe a BIG box and a couple 4" ABS pipes would do it….). A couple hundred $ would motivate me to pull it out to see if its still all there and send it along to you. Then again, you got me thinking of doing this with my grandkids. However, let me know if you are interested and we can talk. All the best to you and your son's
project, very admirable.
Eric