I second Snap Circuits although my DS8 wasn't as "in" to them as I had hoped. Many kids love them. We're going to try Little Bits this year because we think that they might be more free form/ creative.
That has always been an issue with choosing science/building/logic toys for my DS. He's big on doing his own thing, and not much for following a comprehensive set of directions. I mention this because science kits like Snap Circuits are expensive and it was a bummer when he wasn't very interested.
For building, we're getting the Zome tool creator 3. I don't know how well it would work for smaller hands, but I expect to get a lot of mileage out if over break.
https://www.fatbraintoys.com/toy_companies/zometool/zome_tool_creator_3.cfm
