Actually, you should be feeling overjoyed about this trip. By renting from offsite, your husband will have the
scooter 24/7 so he can just drive it around the entire time. Plus - you'll have space to store any purchase you make and your husband won't get tired. He'll be able to use any queues that are accessible so you're not going to be getting special treatment and the Cast Members are great with helping people in scooters and wheelchairs. He can transport from the scooter to a ride vehicle so all is good for that.
The only thing I would highly advise is once you have the scooter is for him to practice backing the thing up. And stopping quickly as some guests don't realize there is a scooter nearby and can walk in front of him without really seeing him.