I have an answer from help99. They "can give a stripe api to integrate". Do the programmers reading this know how to handle that? I'd have no clue, I have to admit.
The #PunchPutin game is nice and actually quite what I was thinking of, though without punching ball, without choosing character and without directly connected donation. But it's a good example of how this could work.
What do you think, @gimulnautti and @stux