ww, i don't know much about your situation, but I agree with what the others say in that you are a good parent and that your children think so too. You may think you have failed them, but remember that you can't be with them 24/7 or they are suffocated and can't develop properly. To me, it sounds like your children too accept that you did the best you could: what happened seems to be beyond your control, so you couldn't have prevented it.

Hope this helps.