Some of the EE pay monthly plans do include USA roaming. The plan I'm on does as it's one of the monthly Smart benefits I can pick from.
None of the UK networks will include roaming in the Caribbean.
Make sure you disable roaming when on board the cruise ship as that is always insanely expensive! Stick to just using WIFi.
Whilst I've not tried them,
Airalo seem to get good reviews and Martin Lewis mentions them. Airalo are also listed on cashback websites as well (TopCaskBack currently offering 15%).
Having looked at their packages, which look reasonably priced, you would need separate ones for Northern America and the Caribbean as their global plans doesn't cover both unfortunately.