Can you change the time of day and get out for a short bit? First thing in morning or very end of day might be better (no idea what time is best). Is your group old enough to go for a short walk instead of playing outside?

As much as it sucks I think families will understand why you need to stay in. I find on days we stay in it helps to pull something new out to entertain the kids...doesn't need to be much just something novel to refocus them. If needed it might be reason for a movie day...I don't use tv at all in my daycare but it would be times like this that I pull out a laptop and pop on a short video (letting parents know what and why). I think all parents should understand that you have lot of factors against your control at play here and things need to adapt to survive!