Advanced Camp for MS3s sounds a lot like LDAC, last held five years ago at Joint Base Lewis McChord with the stunning vista of Mt. Ranier in the distance.
Anyway, there is likely to be a long patrol exercise with little opportunity for hygiene. In advance of this I sent a box of baby wipes my son could share with his squad. I don't know if food restrictions have been imposed but as a dutiful helicopter parent I once stuffed a box with loaves of Wonder Bread and jars of PB and J. (don't forget plastic knives), which he and his squad devoured. Another time I sent a box with about 50 packets of skittles, which was shared among the platoon. Finally, in the spirit of Slim Pickins in Dr. Strangelove, I sent a box with some Mexican pesos, some Canadian dollars, maps of Canada and Mexico, a condom, a tube of lipstick, a can of breath spray, a menu from a fancy New York restaurant, and other stuff likely to amuse or piss off a tired, hungry cadet.
If you do send any boxes, use the Post Office's free Priority Mail boxes. They're cheaper than if you pack your own box.