I think it depends also on the impression that those people give you, even though I've seen intelligent well to do people becoming idiots once they started twisting a throttle and I've witnessed it multiple times.
Well, one thing that you can do is that you can limit the power to something not crazy and let them trying it; it's also a good way to help Stark Future and, ultimately, ourselves. Most likely, most of them will like it.
On the other hand, I also understand that if someone falls and pierces the battery falling on a rock, it will be quite a problem and that it's your right to choose not to let them riding it. In this case, I suggest that you don't let anybody trying it or it will look rude to anybody who won't be allowed to.
Don't you forget though, that, as far as I know, the referral program is still valid. If you mention it to those people and any of those people ends up buying a new bike, you can earn money.