I like the recurring charitable donation thought, especially if it was a donation you would be making that way anyways
We've already lump summed our planned donations through a donor advised fund for tax reasons, but this is something I might think about. It would just be more forced giving :)
My only worry would be about the efficiency of small recurring credit card transactions and small donations vs one large non credit card donation towards the charity. Presumably this is a charity I like, so I don't want to nickel and dime them. But from what I understand, charities like signing you up for recurring giving.
The approach for us has so far to wait for a tradeline sale, and then when it goes through walk over to a grocery store and buy something small with that credit card. The grocery stores seem to post relatively quickly, as opposed to other establishments, and we usually try to be in walking distance of a grocery store. It has been tricky if we've been in the middle of travel/transit when a tradeline sold, then we have to hope to find reliable internet, make a purchase, hope it goes through in time. Etc. No missed sales yet because of that, but some close calls.
The safer thing would be to make regular purchases on the first of each month with every enrolled card. Amazon gift certificates or what have you. Our cards are sufficiently sock drawered, and our sales few enough between, that I've been willing to take the risk and extra effort (and I have time on my hands and I like taking walks to the grocery store ).
If we were making regular sales on a high enough percentage of enrolled cards, I'd consider changing my approach.