I foster, and always seem to get a new kid the week of Christmas. I have learned to buy an extra of everything.
TRU has some bikes on clearance now, as well as an extra 50% off. My store had a basket full of video and computer games.
Also consider labelling things for the "game room" that way the gift is for anyone interested.
Family dollar has name brand hand held games for $5.00, (extreme Bop-It, etc)...great deal!
You have the boys at a hard age to buy for, anyway! Just know that this will be their best Christmas ever, reguardless of gifts, because they are comfortable, loved, and worry-free!