Bathtub paints are the epitome of good clean fun! My son LOVES to paint during his bath, and the best part is that it’s soap! It rinses right off without any staining.
Of course there’s always the good ol’ squirt bottle or squirt gun fight. Outdoor use recommended.
Got balloons? Fill them with water and have a water balloon fight, or put in a tiny hole with a pin, and squirt each other. Also an outdoor activity.
Soap Souffle made with Ivory soap bar in microwave for 1 minute is a fun and clean experiment. Actually, Steve Spangler has a bunch of experiments for kids (and adults) to enjoy that you can do right at home with a few household items.
Have the kids pour baking soda into vinegar to listen to the bubbles. You can use solution this to clean (see my cleaning guide)!
Often when I’m cooking I let my son “wash” dishes. I get a tub full of soapy warm water in the sink and throw in plastic cups, measuring spoons (anything plastic works). He stands on a chair and uses a wash rag or sponge to wash them all. This activity lasts him at least 30 minutes, but can get a bit wet if you allow it.
While you’re letting them play with water, let them give their dolls or toy cars baths.