Hi Betsy,
We have had pretty good luck leaving the plastic bags on when packing for a cruise.
We really feel like it prevents wrinkles to some degree.
To that point , I actually save the bags from the dry cleaners and try to place a bag over
each and every piece of my “ better “ clothes aka evening wear , collared shirts , slacks etc.
My wife does the same with her dresses , blouses and slacks.
One last little thing, we also try to keep these items on the wire hangers from the cleaners, so when we unpack all we do is hang them in the closet.
Hope this helps, good luck 🍀 and have a great cruise 🚢