Rebooking is the best, so that's great, @M199 . As my 2021 dates are nearly completely gone, I'm offering to open up 2022 dates for them if they want. I did that for a couple of the April bookings. But cancelling makes the most sense for most of them -- with all the uncertainty.
My timeline is this: I write through the messaging. Wait 3 days (if there isn't a rush), then write again to say I will be texting or phoning. They tend to answer immediately at that point, but if not, I text. If no answer after a day, I phone. Some ask for a few days to think about it or ask their girlfriend or whatever. I give them that.
I would only go ahead and do the cancelling myself if we were getting down to the wire (24 hours before check-in in my "flexible" case) and I was really afraid they might keep the reservation with all the trouble that would entail. So far it hasn't got to that point. In one case I wrote something like, "It looks like I will have to do the cancelling for you. I really hate to take away your options like that," and, bam, the guest cancelled. Happily, he didn't want me making decisions for him!