I worked ina day care for four years in college as well as babysat. Here are a few ideas.
Carwash-either in sink or a tub of water. Give them a rag and cars (or any toys to clean). Will entertain for a LONG time and will also get toys clean.
You can also put rice or noodels with cups, animals, sppons etc to explore.
Make a big banner. Craft paper can be bought on a big roll and outline something (Happy birthday etc.) and have them paint, color, collage, glue etc Then hang...
Bake, cook, make fruit solad,
And play outside, every day, if only for 10 minutes. It will exhaust them all and fresh air is great!