How about a Weeping Willow? They grow fast and are beautiful. You need a large area though.
Willows have a problem: They can be extremely destructive to pipes, and in a good blow, they go over pretty easily. I think their roots are wide, but not deep.
I do love willows, though. When I was a kid and lived in Virginia, the house across the street had a willow, and we would go and grab two branches, pull one under your butt from the right and grab it with your left hand, and do the same with another, pulling it under from the left and grabbing it with your right hand.
We could then swing, and bounce up and down. I guess it is something you can only do when you are about seven years old!