I splurged £405 on a Euromex ED.1805-S EduBlue. It's a stereomicroscope with a built-in 3MP camera, not as expensive as a Leica EZ4W, A60F or Emspira 3, which is what I'd get if money were no object, but still decent quality and a step up from the realm of toy USB microscopes like my Celestron 44302.

Compound microscopes are much more fiddly because you need to prepare slides, and thus less versatile and less interesting for kids, but that's what's required to view blood cells or fine detail.