Give your children another cup or small picture of vinegar and watch.
A fun chemical reaction with dramatic and still safe effects. and your kids can do it all. If I was really ambitious we would have made some kind of volcano for this mixture, but we did the quick and dirty version.
Allow your kids to spoon some baking soda in the bottom of a cup (or 2). Put the cup in some kind of pan/container with an edge to save yourself A LOT of clean-up.
here if you or your kids want the details. "What actually happens is this: the acetic acid (that's what makes vinegar sour) reacts with sodium bicarbonate (a compound that's in baking soda) to form carbonic acid. It's really a double replacement reaction. Carbonic acid is unstable, and it immediately falls apart into carbon dioxide and water (it's a decomposition reaction). The bubbles you see from the reaction come from the carbon dioxide escaping the solution that is left. Carbon dioxide is heavier than air, so, it flows almost like water when it overflows the container. What's left is a dilute solution of sodium acetate in water."