Some kids get interested in coding by using it to control physical objects. There are some pretty cheap "robot" kits on Ebay, Banggood, Ali Express and similar. "Robot" is a really bad name - they are really just small battery powered cars that can be programmed to move in certain ways.
This kit is about $25 including shipping and includes an Arduino microcontroller board.
Tracking Motor Smart Robot Car Chassis Kit 2WD Ultrasonic For Arduino MCU Sale - Banggood.com
So depending on the age and ability of the kids, they can start by building the kit and wiring the motors direct to the battery to make it drive, then add some simple Arduino code to make it drive forwards, turn left, and repeat to drive it around a square or triangle or whatever; after that the kit comes with an ultrasonic detector, so you can program it to stop, back up, and turn to avoid obstacles; then you might want to add some other cheap sensors (photo diodes) so you can program it to follow a track drawn on the floor or similar.
Obviously you can take it as far as you want, but for the kids that are most interested in this kind of kit, it gets them started in using Arduinos or similar to control stuff, and then hopefully they'll come up with some ideas of their own of other things they'd like to try to build/control.
Arduinos are a good starting point as with just a few lines of code you can make lights flash, servos move and so on, but they're quite capable things in the right hands. There is a really strong on-line community with loads of example code and ideas for projects available. You can buy them on Ebay for a few dollars each so it doesn't really matter if they get fried by accident - they're tough little things though that you can't really hurt by programming mistakes and they even usually survive when wired up wrongly.