Thanks southendcruiser, this is what I was worried about.
I think they also did a Coast Guard inspection on the Oasis upon her return to the US. I remember getting texts and phone calls from Royal Caribbean a couple days before the cruise to not arrive early to Port Everglades. I arrived at Port Everglades after hotel check-out as planned. Although I had to sit for a long time, at least I got a seat and boarded the ship as soon as possible. Last October on Norwegian Escape in New York she was delayed arriving due to a storm in New York the day before and then had a Coast Guard inspection. I had just ran 5 miles through Central Park in a race and was waiting in line to check-in when the terminal became full. Standing in the same spot for a couple hours was not fun as they stopped the check-in. I could see the crew muster drill with the Coast Guard take place from inside the terminal. At least the Serenade is much smaller compared to Oasis and Escape.
As for The Key, I think I'll pass this time. The carry-on luggage delivery to stateroom was the one perk that would influence my decision. If there's a good chance boarding will be delayed to 1PM or later and staterooms open at 1:30PM, then this benefit would be lost, and possibly lunch at Chops Grille.