I understand how you feel about disinfecting everything. It is totally exhausting. In my daycare if parents want to bring their kids sick that's fine but I make it clear they will be totally isolated from everyone else and wont be allowed to join in on anything we do. It does upset me when some of them say that's fine they will bring them anyway. It makes me feel like they don't care about their kids and I feel sorry for the children. As for picking them up late when I call when they are really sick like throwing up and stuff, that's only happened to me once and I ignored it but it REALLY bothered me a lot. So I understand. And I don't think your over the top at all.
Another thing that really bugs me is when my family is affected by their sickness. That's why I also put in the rule that the kids are not allowed to be all over the house anymore but in the special designated daycare area. If parents don't like it they can go somewhere else. My family is more important.