@Catherine2614 As others have noted, you don't need to worry about leaving a review. Skipping it would make the most sense in this instance. Although, if items were damaged (regardless of how/why they were damaged), you are being very generous in donating your expenses to mitigate the damages to this family.
Changing gears a little. . . Now, I'm an ultra pragmatic, business-minded (some may even say slightly ruthless) person. So take these thoughts below with a 10-ton block of salt.
What I find puzzling is that the guests shared this information with you at all. I mean, we periodically travel with my extended in-law family (my wife has a 97 year old grandfather that travels with us). And if he were to tragically pass while we were vacation at a STR, I guess the very last thing we would do would be to share this information with our host.
We would take care of our dearly departed, vacate with haste and be the most respectful guests we could. I just don't know why these guests (or maybe people in general?) can't be private about what's happening with them while still being professional/courteous with others that need-NOT-know.
What's the purpose in telling you? Were you supposed to call the hazmat squad? Are you supposed to inform future guests of the recent passing in your listing? I know that in real estate sales, one of the big disclosures is whether or not the prior owner/occupant passed away in the home (this can dramatically decrease the value of a home). So now you're a bad host if you don't disclose this to future guests? How long from now does it "matter" that someone passed in your listing? Oy. . .
I dunno. I just don't think it's anyone's business other than the family's and I find it really odd that they would tell you.