Sounds great Craftybug. Or, if you didn't' want to do that much applique, you could fussy cut squares of the football, helmets, etc and add red/white or blue borders to get to the size of square you want, then sew it all together.
(But then, I don't have a clue how to applique) I know that anything you do will be great and your DS will love it. Congrats to him on A's & B's. Tell him to keep up the good work!