I haven't been doing this very long (almost 6 months) so I haven't ever closed. I never used to stay home from work either, though, so I always just manage to get by. I don't think you did anything wrong, though. I would have done the same thing.
In fact, I kind of wish I could right now.
I just took my own temp (which I never do) and ironically it was 100.3. I am afraid I might have strep and have worked with it most of the week. Oops! I've been a bit stressed this week and, not smart of me, but just realized that I've had a headache, nauseousness, and a really sore throat most of the week. My hubby couldn't sub for me this week, though, because he just had surgery on Monday and spent the first half of the week in the hospital. Not like it really matters, I would have given the parents the option to come or not, and I'm sure they would have all come. I have one family that mom is out of town and dad is an attorney currently in a trial, another that mom is 35 weeks pregnant in preterm labor and mom and dad are both sick with nasty colds, and the last that dad is JUST starting a new job and mom has been in mandatory meetings. I also was closed on Monday for my husband's surgery, so I would not want to close again the same week. If I would have closed, I would have caused a lot of chaos for all of them. It's not like I would have spent the day resting, either, because I would have still had my own kids and my poor husband to take care of. And, I agree that adults are MUCH better at keeping their germs to themselves. I promise not to spit on them or lick them or anything, and I'm an excellent hand washer. Nonetheless, I suppose an urgent care visit is in my near future, and if I do have strep I will of course let them know.
As far as telling the parents, I would probably tell them. They wouldn't care, though, because my husband is a great sub and the kids like him better than they do me! In this case, I don't think you'd have to tell them unless you think someone would be upset if they didn't know. The kids will probably tell them anyway.