My 7 year old son came home from school and said they played tennis in PE at the local park which I know has full size tennis courts. I was going to buy a couple of rackets (Junior size) and take him again. However, my friend said it was probably short tennis they did. Not sure what this is but if I buy short tennis bats and ball would we then be able to use these on a full size court at the park. What's the best rackets to buy and balls too?