Hi adrienne, I was hoping someone with more knowledge than I would answer you. This is out of my area but I might suggest you try using the find button on your csreen and searching them port by port. There is enough info in the search files from almost any topic to provide some valuable information.
If I book anything I do it on the ship and sometimes on the day of arrival at the port. I like to see how I feel and what the weather will be like. I also like to talk to others at my dinner table and get their feedback. Sometimes the person at the excursion desk aboard is helpful and knowledgable and sometimes they're not, but I like to ask if it's worth a hoot anyway.
I know, I know, there are a bunch of people who will tell you this is terrible advice, all the good ones will sell out! In my experience that's sales hype on the part of the cruiselines that many people parrot. Do things sell out, yes, occasionally. I've never found an excursion I couldn't live without or find something suitable to do as a replacement. Often when I explore on my own I have a better time and usually spend a fraction of the excursion cost that way.
Hope someone else can provide you more usefull information.