I think a policy of having more than one person present in these kinds of meetings, especially if they are off site or after working hours, is certainly a good way to mitigate any risk as well as ensure everyone is still receiving the support or mentorship they need.
As an aside, it's always nice to hear someone who recognizes they aren't a good fit to be a manager. I'm not sure I would be good at it either but it seems that even people who very obviously don't have the personality for it tend to jump at the opportunity.
What if both parties collude against you? Then you're in even more trouble.
I don't get this paranoia against mixed gender one on one meetings at work. You're truly paranoid. I hope this is only a problem in the US. I have never heard of it in Germany or Europe.
Do you really have an Anstandswauwau (chaperon) standing by? I would feel very weird participating only because a man and a woman cannot be trusted to behave professionally in a work environment.
Much less damage scope. Individuals can be vindictive sometimes. especially if they feel slighted, and have easy opportunity. It's generally curbed if they know they won't get away with petty revenge.
I speak from experience from being around vindictive people.
As an aside, it's always nice to hear someone who recognizes they aren't a good fit to be a manager. I'm not sure I would be good at it either but it seems that even people who very obviously don't have the personality for it tend to jump at the opportunity.