Shhhhhhhh ... DD rides her electric scooter without a helmet. I know. I hate it but she wasn't riding on the street when she got the scooter and the helmet seemed over-kill. Now that the only place she really can ride the e-scooter is the street - and a busy one at that - the helmet will be mandatory and she'll understand / agree.
She isn't allowed to ride her scooter with flip-flops on so bare feet would definitely be a "no".