Our grandchildren who are 6 and 8 have always played for hours in the UK on sandy beaches so I was a little worried about them getting fed up on stoney beaches when we took them to Corfu for the first time a few weeks ago. Don't worry, they loved it. We took them to Acharavi one day so they could play on a sandy beach, but they complained and wanted to go back to Agni where they could attempt to throw most of the beach back into the sea and also try to catch the fish with their fishing net.
The reason for the stones on this coast is the protection from the weather due to its proximity to Albania. This means that the sea is much calmer and safer for the children to play in. It's supprising what children will find to do when they have a beach and some water.
Take the bucket and spade. They will always find some sand on most beaches.