We bought our trolley tour ticket directly in the port and it worked great and at a good price (usd 20 each 2 days).
We didn't find so nice the beach in Key West, the windy day didn't help but the water didn't look so nice. The algae crowded along the coastline were pretty disgusting and the smell was bad.
The bus and shuttle lanes were very organized and never crowded, we arrived to port at noon (departure was at 5pm) thinking it would take a while to get onboard, we were wrong.
We did not like Nassau, but we loved the Atlantis resort, it was like a different world on Paradise Island. I would recommend everyone to buy a day pass and spend your time visiting that place, you won't regret it.