Posted: 06/05/2014 at 14:28
I can't comment on the grass but we have small children and they love our paved path that goes right round the garden. They use scooters, bikes, trikes and the go-kart to go round and round. There is also a bit of a slope (about a foot and a half drop) at the end which is good for launching off and might be appreciated when we get to skateboards and rollerblades.
You could make a raised area that makes it more interesting and incorporates a path and slope. I'd have some hidaway areas with big plants in flowerbeds and not just have a very large amount of grass.