Not sure if OP is aware, but
DCL's current policy, here, would give you 100% FCC if you tested positive within 14 days of your sail date:
Book Your Next Cruise With Confidence and Peace Of Mind! | Disney Cruise Line (go.com)
Wouldn't help on the flights, I know, but for that I would just be sure to book refundable fares or an airline that allows last minute changes. And as mentioned, it is future cruise credit, not a refund, but nobody else would give you a refund so better than nothing.
But I suspect OP's plans are going to be dashed even if both cruises sail because given OP's name, seems likely she has kids, and kids are not vaccine-eligible, so OP will almost certainly need to get Covid-19 tests for the whole family in advance of the second sailing, which, given the short turnaround time between them, seems next to impossible.