The kids will probably have never made a ‘rubbing’ before, so it will be new and interesting. Just take a variety of coins, fairly heavy white paper and their crayons and colored pencils. Minimal set up and virtually mess free.
After the art, have the child match the rubbings to the coins and write down the values of each. Move on to how many pennies in a nickel, etc. A sneaky way to get in a little summertime math.