Here are some suppliers in Alberta/Canada that sell airsoft stuff:
http://www.007airsoft.com/instock.htm
http://www.airsoftparts.ca/store2/index.php
check out the Airsoft Canada forums for deals on used guns and check the forum stickys for info.
http://www.airsoftcanada.com/
When it comes to airsoft guns there three diffrent types, gas, spring and electric. By far the best is the electric, also known as an AEG (Auto Electric Gun). Most guns come stock shooting between 200-300 fps. They can be upgraded or downgraded to shoot between 100-500+ fps. The advantage to the AEG is that it can shoot single fire and full auto. A battery powered motor drives an internal piston that "fires" the BB's. There are diffrent weights in BB's and the .12gram cheapies from walmart suck in AEGs. Buy the quality .20gram to .25gram BBs for better accuaracy.
If you purchase a cheap brand like Kraken or Jing Jong, you will end up replacing the whole gun or the internal parts within a few 1000 rounds. Stick to brand names like Toyko Mauri, G&P, Classic Army and Systema.
Now if your son is young i wouldnt recommend getting him and AEG. They are 1:1 replicas of real firearms and he can easily get himself in a world of sh** real fast. there are numerous stories out there about kids with airsoft guns getting into alot of trouble. dont get me wrong i think airsoft is a great way for a kid to learn about guns and how to properly handle them. treat airsoft guns like a real gun and you shouldn't have any problems.