Here is a super fun, easy, and cheap activity that will be a BIG hit with your kids. Named "the ice trick" by Moses' friend Keefe who taught it to us, all it requires is food coloring, water, and a bunch of different sized containers that are freezer friendly.
Fill all the containers with water and have fun adding different combinations of food coloring. Two is definitely too young to fully grasp the idea that "blue and red make purple," but you should have seen Moses' eyes light up when he stirred those two colors together and they "magically" became a different color all together!
This is a kind of messy activity, and I haven't quite figured out how to avoid getting food coloring on your hands, but Keefe's mom assures me the green washes out in a few days. :)
Put all the colored water containers in the freezer and (here's the hard part) wait for them to become huge colorful ice cubes of all different shapes and sizes. We're still in this phase, but I've promised Moses that after his nap he can play with them in the tub. I'll let you know how it goes...