Our wedding group is booked on Westjet for February. There are no unusual restrictions concerning luggage so I'm unclear to what you're referring specifically. We've been to Jamaica a number of times before.
Packing should be relatively easy ... the weather is consistent (except for the possibility of hurricanes during that timeframe). 2 tanks, 2 shorts, swimsuit, a sweater, a windbreaker, 1 pr long pants (cotton, linen or zipoffs), perhaps a dress in case you want to go to the specialty restaurants, running shoes and sandals or flip flops. Clothing for a couple should take up about 1/2a normal size bag for a 2 week period. Balance of the first suitcase is toiletries, etc. 2nd suitcase = wedding stuff (or split them 1/2 and 1/2)