In the past we have packed the extra large ziplock bags and bubble wrap and tape to protect the bottles in our luggage. We would then surround it in the middle of a bag with clothes to further protect it from getting tossed around. We didn't bother this year though due to the hassle of getting everything done the morning of as we were doing an early walk off to make sure we made our flight and didn't want to have to deal with trying to quickly pack it that morning.
DCL needs to rethink this and go back to delivering the booze the night before to allow people to properly pack it, especially for those having DCL deliver their luggage to the airport.
Next year we will have to figure out how it is handled on RCCL, because we are going to St Maarteen and will definately be purchasing some guavaberry rum and liquor. This used to be easy on DCL, but we would still deal with it for the guavaberry stuff, it is really yummy