I'm not completely sure of the whole procedure, but this is what our son (a current 4*) did this past fall with the USAFA-USNA game. There were no classes the Friday before the USNA game; he applied for a "Triple S" type leave/release and was granted it. He flew to VA late Thursday evening on a commercial flight he paid for (well, actually arrived early Fri am), spent Friday at home, Saturday drove to the game, came home from the game Sat night, flew back to USAFA Sunday morning.
The interservice games are very popular so 4* often don't get on the list to spend the night at the sister SA.
As for football tickets -- those games sell out -- so, yes, you might want to get the tickets early and then if your son doesn't travel to the game you could probably sell them. I saw lots of requests for tickets on this forum & CC last fall.
But -- don't jump the gun on things yet. Your son hasn't even inprocessed - nor made it thru BCT. You really can't plan too much until that happens.