I totally understand the concerns that go with parenting while disabled - my wife and i dont even have kids yet and we are already working on how I will transport them as a full time wheelchair user. I know an infant can be put in a sling-carrier and certainly not mess with driving, but I dunno how to do it safely after that!
I use either a manual or powerchair, so it will be a little different than an
ECV (where the child is between the driver and the controls). My sister is going to come up with a stroller for me that attaches to my wheelchair (she's an engineer), which
technically is against the rules of Disney, but we'll have to see what is allowed.
there are a LOT of challenges to being a parent, and some of those are doubled by being a disabled parent. But putting a child on an ECV with the person who is driving it is dangerous to the driver, the child, and the people around them.