Your morning airport arrival won't be chaotic...morning arrivals are generally less busy.

Mega Mart should be open on Christmas day in Montego Bay...I'm not sure if Progressive or other stores are open there. The HiLo and Value Master in Negril is closed...so if you see a store in Montego Bay that is open...make sure you stop.

The only rock climbing experience in or near Negril that I know of, is located at Jamwest... https://www.jamwest.com/