Answer:
There is no age limit or requirement. The person operating the scooter must only have the where-with-all to avoid injuring themselves and others.
Better check with DMV. A mobility scooter in not like a regular scooter. Last thing I saw about age with a mobility scooter WA age 62. I have been doing a lot of research in referance to license requirement without much luck on the subject. DMV handbook states you must have a DL as of July 2010.