The 25 has more versatility as a dual purpose than the 22-250. If you braked the 25-06 your boy should be able to shoot it without a problem.
It all depends on what primary purpose you want it for. the 25 will tear up fur more over the 22-250. Get a 17 Rem., 17 Mach IV, 20 BR or 20 PPC for fur & a 6.5-284, 260 rem., 250 Sav, 250 Sav AI, 25-06, 284 or 243 AI for deer sized game. Some of these cartridges also work good for elk.