what could i do about it? of course i can send an identical offer to my guests w/explanation, but i dont want to have this cancellation on record on airbnb (the first in 5 years, 5 houses) and dont want to have the calendar blocked for those dates.
You need to contact Airbnb if you need to reactivate the reservation you accidentally cancelled. I would definitely write to the guests and tell them that it was cancelled in error and you are working with Airbnb to correct it immediately. Ask for their patience since it might not happen fast.