Are you looking for ways to keep your elementary-aged kids engaged and having fun, while possibly learning something at the same time? Why not let them try exploring some scientific concepts -- they can do these on their own, or you could get involved and have some fun together.
The STEAM Quest kids at our Bath Branch had fun creating a lemon battery. Though they had to persevere and try several different configurations to make it work, that's half the fun of science experiments! You'll need at least one lemon, a galvanized nail (or something similar coated in zinc - paper clips will work in a pinch), copper wire or a penny. Optional: additional lemons, alligator clips, small LED bulb. You can download the instruction sheet here.
When you're done, you can use the juice from your lemon to write secret messages - once they're dry, hold them under a lamp to expose the writing.
How does snot work? We may think of it as a nuisance but it actually has a very important role to play in keeping us healthy. Follow the instructions here to make your own snot, and experiment to see how it protects us from germs. Side note: if you don't have plain gelatin, Jell-O might work.
Wash your hands! That seems to be all we hear these days, but having your kids do this experiment (which also doubles as process art, so is twice the fun!) will demonstrate what the soap does when it encounters the out fatty layer of a virus on your hands. All you'll need is dish soap, milk or cream, food colouring, and a shallow dish or dishes. Check out the full instructions here.
When you need more ideas, check out the Let's Talk Science website for more ideas, complete with grade levels to help you match them to your child's level.