In Nassau, the excursion you mention is an easy self guided walk (we did it in a few hours). The Unofficial
DCL book has a great walking tour map and guide of Nassau. It's $96 you don't have to spend.
Check the DCL site FAQ and your paperwork when the booklet arrives for all your check in needs. It's all there in one spot and has the Disney policy for nearly everything in it. Was reading online this AM about a lady who was 25 weeks pregnant and (like it or not) the policy of DCL is no women past 24 weeks can sail. I remember reading that when I made our most recent payment for Alaska and it showed up online in the email receipt. I kind of chuckled at the strident warning that there were no exceptions and whatnot.
Check with DCL online and if anything is ambiguous, give them a call. Don't want to be like that family from St. Louis that couldn't board because they were unaware/didn't read the rules.
And no, I really don't want to start a hare about the legitimacy of the rule, I was just using this as an example. The boards are great and there are some very knowledgeable people here who've done many cruises, but in the end, it's DCL policy that rules the day. We've done 7 cruises and have 8, 9 and 10 booked and I still call DCL for clarification on issues.
For example, here on the boards we were kicking around the idea of using a popcorn bucket from a previous cruise. Some people have reported success in doing so, but when I called DCL to confirm, they said that reusing popcorn buckets is not allowed. So, the people who had success were out of the norm, I guess.
The point: look on the website and/or call DCL and look there for the official policy/rules