They are right about no minors renting from DLR but minors may bring their own
ECV or rented ECV into parks.
DCA and Downtown Disney as well as hotels are very easy to use an ECV.
Disneyland has sidewalks in Main Street which get jammed and the trolley tracks are not a problem until you try to avoid idiots.
Pirates requires going against the exiting crowd which is a pain even if you are a linebacker in full uniform and using a cattle prod. It is up hill and people are exiting into the bright sunlight at times.
Splash Mountain requires going into the area where the ride pictures are and then through to the ride. Same problems as Pirates as you are facing exiting
ECVs, harried guests, and wheelchairs.
Trains are fine but you cannot get off at Main Street Station if you are in an ECV or wheelchair unless you want to hand drag the chair or ECV off the train and down a long flight of steps.
Space Mountain is not too bad but it is way way in the back near the cast entrance.
Most rides you have to use the exit to get in. All rides except the train, Small World and monorail are not wheelchair on the ride so you have to transfer.
The park is much narrower so there tends to be bottle necks like from adventureland to main street. Nothing like Fantasmic to end and a thundering herd of people exiting. Even a walking person can have problems if they run into a bottle neck.
Some restrooms are almost impossible to use a wheelchair let alone and ECV in.
It is not something to miss as DLR has worked hard to help the disable use their west coast parks despite their antiquated nature.