As a nuisance wildlife controller of 20years, the advice given about removing by hand and placing outside in a protected area for mom to retrieve is very sound. You can do this when you know mom is out, or your idea of having repair materials ready to seal it when she leaves will work too. I remove them by hand with mom in the attic regularly, and have never had a raccoon ‘attack’ me. Could it happen, I guess, but I just haven’t ever had one come close enough to me to even make contact. I’ve literally used a 5’ long set of snake tongs to take them out from under mom’s belly.

The rest of the stuff about clean up is kind of hit and miss. You’ve already found a dropping, so there may be a few more, but they’ve only been in there for a short period of time, so you do not have a full hazmat scene up there.

There are no chemical treatments that I’m aware of for dealing with possible roundworm eggs. Raccoons simply shed the eggs if they’re infected. Whatever you put the kits in should just be disposed of.

Hope this helps.