I've done a little bit over the years, a couple of times with my kids. A breadboard kit with some LEDs and resistors is a great way to get started for 4-7 year olds. Older kids might be able to handle soldering and/or programming a micro.
Check out adafruit.com they have a lot of beginner friendly kits and projects most of them have tutorials to go with the kits.
https://www.adafruit.com/explore/beginners-gift-guide-100-or-less
