Gosh, if he has no food restrictions the possibilities are endless. I'd say home made chicken soup with meat bawls or is it bolls or balls, well what ever the spelling. Get the whole or cut up chicken. Use dark meat and bones to make soup. Put the white meat thru the meat grinder, if you do not have use food processor, but meat grinder is preferred, grind together with one small onion, and 1-2 slices of white bread (soaked in called water and squeezed). Add 1 large egg, mix everything together. Salt and pepper to taste. Form small bawls (SP?), maybe 3/4". When soup boils and you pick off the dirty foam on the top ad them in cook like you would normally cook chicken soup. Serve. Personally, I like to serve it with a spoon or two of rice, added right into the plate. Rice cook separately. This is very nutritious meal. It will have protein and veggies, and it is easy to swallow, practically with out chewing.
That is what our son ate for the first week after he had his braces