We have a unit owner who rides his motor bike a short distance along a common property foot path before taking it down a short path into his private courtyard. He does this carefully at walking pace and I am not aware that any of his neighbours have a problem with it.
The only issues I can think of would be if your bike rider were not so considerate and careful or if there would be a tendency to create an ugly worn track across the grassed area. Could the rider take a route that was entirely paved?