While they may allow you to charge an outside rental at the in-park rental location, I would consider your logistics. What will you do during that time the scooter is charging? The in-park rental location is at the very front of the park, most folks don't return back that way until they are ready to leave. For example in MK, it's a long walk back up Main Street to any of the "lands." IF you find yourself in a situation of needing to charge in the park, it's probably easier to ask at a restaurant and let it charge while you eat. Or somewhere more central to the attractions the family will be visiting at that particular point of the day.