What are you asking, @Sally550 ? Are you wondering whether you can require masking and vaccinations of your guests? Since shared space is involved, you should have no trouble with that if it is clear up front in your description. You might ask Airbnb, though, to be sure.
Absolutely keep your calendar up to date so you don't have to turn down too many requests re timing. When I am dealing with something upcoming for which the timing is vague, I block dates proactively. Then, when my dates firm up, I open up what is available.
As to cleaning for already-booked guests when you need to be away with your sister, could you hire someone?
Are you worried that Airbnb will shut you down for saying no to requests or are you considering cancelling already-booked guests? I would block the calendar to head off the requests, and I would do everything I could to honour the already-booked reservations. If you cannot honour them (cannot find a cleaner, etc.), see what you can do to get your guests rehoused to everyone's satisfaction. You could start by looking at local listings to see whether they have open dates. You could contact those hosts or try going through Airbnb.
Hope this helps a little. Apologies if I have misunderstood the question.