I purchased these for my son's birthday present to accompany a small scooter he also recieved. He was five - but a very small five. These represent a good protective product and they do have elasticated sides to accommodate many sizes - at a push they would fit me!
At the moment, they are a little big (given my son is a little small!) but I find they fit slightly better over Jeans/jumpers than joggers/t shirt stuff.
I would probably reccommend them for a slightly older (if not bigger) child but I'm sure they will come in very handy non the less!