I tried to reply yesterday, but it seems they are still having heavy load server problems.
they are cheap and you can make music devices with them.
https://projects.raspberrypi.org/en/pro ... c-theremin
and of course other boring things like distance and collision detectors
https://projects.raspberrypi.org/en/pro ... like-a-bat
DS18B20, while you have temp sensor, it not perfect. These you can stick in the ground, liquids, the air and check against the SenseHAT to create a compensation setting to correct the SenseHAT (maths and reasoning, fun?). If your place is in to STEM ,cross curricular, then they can also be used in Science for experiments. Get the long waterproof probe versions.
And of course robotics kits for simple robots, like car buggies etc. This would then link into BlueDot as you can control it.
https://projects.raspberrypi.org/en/pro ... ld-a-buggy
https://projects.raspberrypi.org/en/pro ... trol-buggy
Have a look at the GuiZero python module and the things they have designed it for.
UK? Senior, Primary
If UK senior go raid Science and/or Comouting for the micro:bit they have (science should have 5 from a The Crunch kit they where sent)
Use the Microbits on their own or to control thing on the Pi.
If you search for homebrew Alexa/Google Voice get a few bit and pieces to make you own assistant.
Also IR trip wire setups, should be good to build a trap or to use as timing gates for a robot car race.