We've had exactly the same op. I have a 4yo and a 2yo both in nursery, so if one gets it, the other does too, but a few days later, so we have a rolling period of sickness. I think since Christmas we've had about 5 weeks where both of them have been in full time all week.
Dd particularly is prone to a high temp when she gets sick, she's the 2yo. And once she gets a temp she's utterly miserable, and I wouldn't ask her to go out and do stuff when she feels like that, I also wouldn't inflict her on other people when she's that miserable either.
Since Xmas we've had multiple colds, one case of covid, maybe half a dozen sickness or diarrhoea bugs (occasionally both). Once her temp goes above 38, if calpol doesn't bring it down in 30 mins, they send her home. If it's on the weekend we don't get to do much, because who wants to deal with someone else's kid projectile snotting when they sneeze? Also, managing a barely potty trained 2yo with diarrhoea is far easier at home. And it's just common courtesy not to spread these bugs. Not to mention the fact that sick kids don't want to be at family parties or days out, and they shouldn't have to be if its not essential.
It's been utterly, utterly shit. Im on an attendance warning at work for the first time in my life. This weekend I have missed my nephews birthday because the kids brought home a chest infection which knocked them and me for six. We missed seeing my dad for fathers day because of a vomiting bug. I picked the kids up friday and dd's room has a sign about a hand foot and mouth virus going around, and ds's room had a sign about a d and v bug doing the rounds of his group. It feels bloody endless.