I like the dollar store idea, set an amount limit and let him shop, will be a 'daddy and son' event, and he might be able to get something that Mom normally wouldn't let him. My 4 yr. old (5 on the 15 of Sept.) daughter loves to pick out her own things. The other thing about doing it this way, is I am going to start having her pick out some old toys to drop off at a shelter or a hospital for kids who don't have these things. Makes buying more less hassle because there's room enough for them, and I don't have to be the bad guy by throwing them out.
As for car tracks, I think Fisher Price has a couple plastic ones with garages and ramps, but they aren't like that one you pictured above with the loops (at least not the ones I remember). Also if you have a basement or spare 4' x 4' area, you and him could build a race track for the cars he already has out of household things like his old Hot wheels ramps, and bricks, blocks, paper towel rolls or use it for his remote control cars and he and his friends can race, tear it apart, make a new course, and race again!!
Good luck!!
