Many activities in Greece can be kid friendly, as long as you make some minor adjustments. The acropolis is a great place to visit but it can get a bit tiring for young kids who don't like being in the sun or walking up a lot of stairs. My first recommendation is to go very early in the morning, or late afternoon when there is not a lot of sun. Make sure the little ones are wearing hats and sunscreen and they are very hydrated. I suggest that you don't spend too much time at the top of the acropolis, but rather take a stroll through the museum and have a snack at the Café that overlooks the Acropolis. As always, you can make the experience more fun by getting some goodies at the gift shop.