You may want to wait til he's a little older but woodcraft.com sells a My First Project tool bag with kid sized "real" tools. I got it for DS when he was 5 & he still LOVES it 2 yrs later. 2 screwdrivers, tape measure, level, really nice sturdy bag. It was clearanced when I bought it 2 yrs ago & still shows that price now. He has taken it to grandma's to show, helps me w/house stuff and used it when his Scout troop built bird houses.
Anyway, just wanted to share because it is such a great product! (no, not a rep, just really impressed w/the quality & price!)