L.H.
For your daughter maybe a massage or mani/pedi. Facial or a cute haircut to start summer? New pair of sandals or a movie night with friends?
For your son I would talk to his recruiter. It might be that you can purchase a bag that is regulation for boot camp. You can always give him a card that when he gets his first deployment you'll help him with what he needs. Personally I think a laptop would still be great. He can take it with him after boot camp where ever he's stationed. A great way to stay in touch.
Tell him thanks for his impending service.