Teaching kids about computers...

So the boy (9yr. old) was asking last night about how computers work... any recommendations for good books for learning the basics from? I think I started out with a Sinclair Spectrum and its BASIC manual, but I really don't recall now where I found out about the fundamental building blocks of [typical] computers and how a CPU worked. There must be a good 'classic' "how computers work" type of book which avoids going on about PCs and Xboxen... I figure I should find him one of those kids electronics projects kits too (I think that was where I got my first exposure to logic gates from at about the same age) and also some old 8-bit machine to play with. I can get a Spectrum / BBC micro shipped over in a few months, but something US-built might be better; any thoughts? I did wonder about a C64, but maybe it'd be better to start with something a bit more simple? i.e. probably something Z80 or 6502-based (just because there's more resources devoted to them), generic cassette data storage, basic video abilities etc. (You know, I don't recall seeing a 'how to introduce kids to vintage computing' thread on here before :-) cheers Jules