Did you end up going on the cruise during spring break? Was it crowded?
As for the notarized letter of permission, I get your frustration. I would not say it would isolate it to just MSC. Our friend was in the same situation and RCCL did not tell him either. He's divorced and did not know that he needed a notarized letter from his ex. He found out the week the cruise was set to sail. I get why any cruise line or airline would want a letter from a non-guardian.