I feel that your son is asking for a "blanket/throw" rather than a "quilt" as you know it.
He doesn't care about it being pieced.
He chose the fabrics and their feel.
Who knows what he'll do with this once he has it....it'll be sturdy as all get-out and can be dragged all over the place (as in a son's mind - outside, on the grass, dirt, lake, truck, picnic, treehouse, whatever).
Personally I'd never dream of doing handwork on such a piece, and if you fancy-piece a border, it'll be for your pleasure not his. Perhaps you should rethink your work and design on this particular item and just make it exactly as he's described and machine-quilt it all the way. He'll be delighted; you'll be much less frustrated; and you can make him a "real" quilt for birthday or Christmas, taking your time (and pleasure)to design and work on it.
Just my point of view; that and a couple dollars will get you a cuppa coffee.
Jan in VA