I'm glad your son hates coloring books-- I think everyone should.
Art supplies are a great idea. Sculpey clay is great, since it doesn't dry out and if he makes something you'd like to keep, you can harden it in the oven. You can also get a Plasticine set with a bunch of different colors, tools, and a mat for cheap. You could bring some colored toothpicks and glue, or get it when you get there, etc.
He might really like some ThinkFun-type solitaire games. We have enjoyed many, including Clever Castle, Rush Hour Jr., and Hot Spot.
Someone else mentioned Choose Your Own Adventure books in a separate thread, and they now even have an early-reader line.
For the laptop, there are a lot of games he might like. My son loves Zoo Tycoon and similar simulation games. If he's interested in space and it's in your budget, you could get a space simulator-- that could occupy him for quite some time.
You could get him one or more models to put together, or puzzles.
