Usually if there's Canadians gaming in the US they'll secure rentals beforehand or buy a gun and sell it before they come back.
Age limits are well 18+ most places but concessions can be made for younger players depending on field owner/admin running the games etc.
Only real thing that Canadians can buy are accessories, gear and such. Mags (can't be clear with faux bullets), scopes (can't be under ITAR), stocks, hand guards, BB's, clothing, gear like vests, holsters etc. (stuff that's not under ITAR).
There are "black" guns available in Canada just not publicly you have to become AV'ed in order to get access (meet with a rep and show some photo ID so they can make sure you're 18+). The clear receiver guns are what most of the big public stores sell.
PS: I have to also commend you for being a retailer who looks out for his customers rather than making a quick buck. I'm sure you get a lot of repeat business.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE