Covid is such a terrible experience even once, let alone five times! I'm so sorry to hear you've been going through this :(
I believe the most concerning part is that we don't really know what to expect in the the long run regarding the repeated covid infections. This would be my main concern, that I don't know in what ways my child could suffer because of it months or years from now.
I am in a similar situation with my 4 year old. He started pre k this September and even though he didn't get covid, he got all sorts of respiratory infections. He goes 2-3 days, catches a virus, and then stays home for two weeks to fully recover. It's frustrating not just because of the discomfort, but also because of all the treatments he's taking and because he doesn't get a chance to adjust at pre k.
Because of repeatedly getting sick, we've been with his pediatrician through certain treatment options that would help strengthening his immune system a bit.
We're also having some extra risk factors that point towards an asthma suspicion, which, again, makes him more likely to overreact to simple cold viruses.
Back to your situation, is everyone getting covid so many times at your children's pre k? If you children are getting it more often ( I noticed you said it was more complicated only once, with the croup), perhaps you could look into supporting their immune system a little?