God Bless you i know how hard it is :( I am sure you all gonna recover and be healthy and live normal life again.
When you are talking about isolation, do you mean isolating at home, or isolating your positive daughters away from the rest of the family?
I think isolating the positive ones away from the others is still a good idea, with one parent taking care of them, and the other parent taking care of the ones who are negative. I think the negative ones should still isolate from others outside the household, though, even if CDC guidelines don't necessarily call for that.
Testing is confusing everyone. I have a lot of friends who are negative on one test, and positive on the next, and vice versa, within a day, sometimes hours. The PCR is the gold standard, supposedly, but there's still a big question mark on things with Omicron.
Good luck. I can't imagine how hard this must be. I hope everyone stays healthy, even if they are positive.