Airsoft Atlanta is run by a bunch of younger individuals that really know their stuff.
Just tell them how "serious" this gift needs to me and how well it needs to hold up and they'll work with you.
Plus they have most inventory on their website.
Their prices could be much better compared to others though but they don't screw you.
One thing...since you're after a gas gun, make sure you get one that uses the standard Green Gas, then ask them if they can sell you a propane adapter (or look online for a cheap one) so you can just use propane from the store to charge the magazines instead of running all the way to the airsoft store or ordering the gas online.
The special green gas for airsoft guns is a mixture of propane and silicone oil.
Make sure when you buy it that they go over the magazine's SOP for gas pistols with your son....because if they don't a $10-$50 magazine can be ruined in seconds. I know, because I've done it.
Hope that helps.
ETA : For 1911's I like WE-tech .