LEGOs suspended in a liquid soap dispenser. Fun to put out at a LEGO party or everyday use in your kids' bathroom! I'd probably search for a cuter dispenser, maybe more geometrical, but still such a cute idea! Also great for the Hand Sanitizer!
Preschool math - counting around the house. Count the number of doors, windows, doorknobs, faucets, etc. Simple math activity that they can do at home with the parents. Make a "map" at school and send it home.