Post Embarkation ideas?

Our flight after our cruise in Miami is at 4:30pm should we go straight there or kill time? What do people usually do and how do you all handle luggage?? We are getting off pretty early around 8 to avoid the uber fiasco we dealt with the last time we got off of Virgin at 10:30am (waited 2 hours for an Uber). We ended up staying the night that night and flew out the next day but this time we are flying out same day and idk what to do to kill time.