I' m sorry for your loss. What a wonderful gift to give your grandson.
For the hunting of deer top pick of your choices would be the .308
I' d get him to the range for lots of fun shooting with the .223 and th Mini 30 in 7.62 x 39, another fun round.
The .308 will be the ticket, but he should soon be able to try the Springfield...if it is in origianl military configuration it may end up being pretty comfortable to target shoot.....might be a little different lugging it aroung the woods.