Age gap + one night stand situation

Sooo If I'm writing this here it means I'm a bit desperate. I've been doing the aupair in Germany For the past 10 months and I'm leaving in 10 days. From the beginning of this experience I've had a little crush on one of my greatest friend's host-dad but It was more like a joke fo me. In the meantime he got divorced and I used to go at his house quite often because of my friend.

Here it comes: as soon as she left he started flirting with me on IG and invited me at his house, and today would be the only night in which I could go there, the fact is that I would be feeling kind of guilty (for my friend, his children and his new "girlfriend"). I've never ever done something like that before, like a one night stand + with a man 22 years older than me. In the meantime I think that I'm 20 and I've had this kind of fantasy for a bit now, but now that I have the concrete opportunity I really do not know what to do. What's your opinion? Thanks for your time and (I hope) your answer.