DIY magnetic silly putty - I am not sure what all goes into it or if it toxic, etc. but the idea of it is REALLY neat. I am going to have to check into that during out magnet unit in science this year!
Considering having the teens make a giant batch of blue glitter slime in our water table and then letting them take some home in baby food jars. Might have them put the plastic sea creatures in the slime too, instead of making the shark jars.