These will be a bit advanced, but I'd like to also recommend Neil Downie's books of Saturday science projects. One example:
Vacuum Bazookas, Electric Rainbow Jelly.... There is a museum local to us that has adapted some of these projects for use with 8-13 yos. I'm not sure how easy you'd find it to do that yourself, but it may be of interest to someone here and I don't believe I've seen the author mentioned here before.
Oh, kcab, that Downie book looks terrific! And I see that he has written at least two more--thank you so much for suggesting him. I'm not sure if I'd be able to adapt them for Groucho myself, but I think I can find somebody around our area who could help (though I might save them on the shelf for a couple of years).
beak, the spacecraft book looks very fun, too--right up Chico's alley, I think. Thanks!
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