Thanks for all the suggestions everyone! I love this forum.

We do have some 'construction' type toys (especially Lego) and he likes those as well but his urge to disassemble is pretty strong so I wanted to help feed that a bit. I was mostly picturing something he could fiddle apart at the dinner table while I made dinner, so I'd step in and help/supervise a little but not do the whole thing with him.

As I think about it more though, I think a lot of the fiddling apart the cars is because he's wanting to play 'mechanic' so he breaks something and then tries to put it back. Just doesn't always work out for him... it doesn't help that his dad is pretty good at fixing stuff and takes it as a personal challenge to get it back together. So my son has a sense that everything is fixable eventually.

Are there any types of small appliances that should definitely be avoided because they contain mercury/strong capacitors/anything like that?