One thing I want to add, is that for excursions, I would recommend booking through the cruise line in advance, since this is your first cruise, and you are probably not familiar with the ports of call.
Also, as this is your first cruise, I would recommend booking through an agent instead of by yourselves through the cruise line's website. I would book ASAP and just keep checking the website in case the price drops. Should the price drop, contact your agent, so you can work out how to get the difference back.
2007 - Majesty of the Seas
2009 - Enchantment of the Seas
2010 - Freedom of the Seas