The 2's really don't get any love. They were my first retro I ever picked up, and one of the pairs that really got me into the game. I would love to see another retro run.
It's something that you can do in most stores, but it can be a **** move depending on the situation. For most shoes you should probably already know your size anyway. You have to realize that you're trying on shoes that someone else is going to buy, and then they're not going to be DS. Plus...
If he's not really into Jordans, I would vote for getting him something simple that's easy to wear with anything. Something in pretty basic colors, in a simple design. I would go for something like an OG colorway 3, or a simple colored 1. The RTTG Retro 1 is pretty easy to find and the colorway...