In Toronto I'm not sure, there are a lot of fields to play on there but you'll have to check with local hosts and ask REALLY REALLY nicely.
I know that FVAA/Big Foot, Low Shotz, EASY, and Ambush Anonymous all do under 18 but you're not really anywhere near any of those groups (they're mainly in the West if you're wondering).
PS: I'm against under 18's and airsoft (hasn't been that long since I was a kid) but if you're safe, responsible and all that I don't see anything wrong with that.
Also, if your parents are willing to join in and stay on the field (in the spectator area) I see nothing wrong with letting you play, it's just some hosts don't like having kids due to liability (even if it's a private host they could still get nailed for liability/due care or w/e) and they also don't like being "babysitters" where the parents just drop off the kid and leave to go shopping or w/e.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE