Yes, you should be fine timewise. If you are scheduled in port until 4 PM, the last tender back to the ship will be 3:30 PM (ship's time).
No, there is no cash bar on Capt. Marvin's boat. Thanks for asking the question, however, it made me catch the mistake in my previous post as I had meant to say: "The Buccaneer has a cash bar available that was not available on Captain Marvin's boat". (I will immediately make the correction.)