Quick growing plants for shade

Hi, 

We've just removed a large hedging plant from the side of our garden that had started to grow into a tree. Ugly as it was it did provide some good shade which is pretty important with two preschoolers who love to play in the garden. What can I plant to replace it that will grow quickly and provide some decent shade? I am assuming of course, that we will be having a Summer worthy of needing plenty of shade!

Thanks