I would suggest that anything you want to make sure you get to do you book ahead. I recently had an experience where we booked an excursion, found out it would be too strenuous for mom and dad so I deleted it and booked a different excursion. The replacement excursion I booked ended up getting canceled a week later and when I went back to re-book the original one for my dh and I it was all filled up...and there were 3 different times...all were full. So if it is something that you just have to do and the only way to do it is through the cruiseline...then you want to book ahead.
Carnival's website shore excursion link will indicate whether each tour is limited, as in number of passengers. If you really want to do a particular one and it is limited, book it in advance. Some do sell out. Otherwise wait until you get on board. At least that's how we play it. But, only rarely is there one that we desperately want to do.
I would recommend booking on line. We have found that some of the tour prices increase when you try to book later or even on board. Happy times!
Sensation (without KathieLee) July 2001
Paradise (smokefree) March 2002
Valor (inaugural season) May 2005
Truimph May 2007
Fascination (1st time w/DD) May 2008
Pride (with DD & DS) November 2009
Book online before you leave. It's easy. Do not take any excursions from hawkers outside the dock. It can be dangerous. It's much safer to have an excursion booked thru Carnival. Have fun!
Irish Ferries Jonathan Swift June 16, 2006 (Dublin, Ireland)
Irish Ferries Ulysses June 17, 2006 (Holyhead, Wales)
Carnival Facination August 4, 2008 (Key West USA & Cozumel, Mexico)
Carnival Valor June 14, 2009 (Grand Cayman, Honduras, Belize & Key West USA)
Shore trips from the cruise lines are becoming more and more expensive. On a recent 38 day cruise the cost of shore trips far exceeded the cost of the cruise. Most people take the position that I probally won't be here again so lets splurge this one time. Taking a helicopter ride in Hawaii can cost you several hundred dollars if purchased from the cruise line. Booking your own helicopter, as we did, cut the price in half thus it was really affordable. We tried to do the same thing in South America where the cost was over $4000 for a Machu Picchu side trip. We found the same trip for under $2000 however with time restraint and the risk of missing the ship at the next port-- we had to forget that shore trip. If you will take the time you can probally find a better bargain on the internet for a particular shore trip than purchasing that trip from the cruise line. If you don't like the risk or want to take then tiem anad you feel it is a must shore trip then book before you get on board. Soem shore trips dod sell out and are not available on board while others never fill up. If you want to take a really expensive fabulous trip try to get some other travelers to go in with you. A helicopter ride is a good example. The cost really goes down when you share. A 100 mile auto ride to an ancient city at the next port might be as little as 25% of the price charged by the cruise line and you will have much greater flexibility in your own motor vehicle. Good luck!