Desertwillow:
I've sent canned air to a couple of units. I sent them parcel post and they got there without a problem. The postal clerks told me it was okay to go priority, but like others have said on this forum, not all the postal clerks are up on all the regulations. I was a bit worried about the cans exploding, so I put the canisters into a smaller cardboard box and secured it with lots of tape before putting it in the larger box with the rest of the care package items.
If your son has a laptop computer, you might consider sending him a lap top cooling fan. It helps keep the computer cooler and blows out the dirt and dust that fall between the keys. I use one all the time and it's amazing the amount of dust and particles the fan blows out. I send these to the guys and they love them. PM me if you want the link to the place where I bought them. I can't remember it off the top of my head. Hope this helps.