A car with the ability to lock down the interface for children/elderly probably does not exist.
I would check out the Nissan Leaf and Chevrolet bolt if those are available.
Dealers are always going to try to talk you out of buying an EV from them. They make their money doing maintenance and oil changes on cars they sell, EVs have no maintenance, so they see them as bad for business. You have to pick out the exact car you want on their lot, write down the VIN number, then go in and tell them that is the car you want to buy. If they try to switch you up just start walking out. Be firm.