I have also sailed on Carnvial and think they offer the best value - good food, good choice of itineraries - although personally I am biased against the 100,000 tonenrs TOO big for me. A week seems too short a time to fully explore one of these vessels. I would suggest a FANTASY class ship on a seven day itinerary as a good first cruise. Carnival offers an excellent product. Don't book with an agent - book straight with Carnival. And after you've booked, keep calling them back every few weeks to see if there are any new promotions. If Carnival puts out a better fare on the accomodation you book, they will give you that price - but you have to ask for it. Sometimes you can get upgrades. There's no guarantee of this, but in six cruises I was able to get a better price or upgrade five times.

My husband and I are also in our 20s and actually took our first 2 cruises with my parents! (It's their fault we're addicted now too!)

I've been on HAL, Princess and Royal Caribbean, and we definitely liked Royal Caribbean the best. Much more fun!!! (Princess was way too "stuffy" for us. HAL was alot of fun, but we still prefer RCI.) My parents just took their first Carnival last spring, and had a lot of complaints...don't get me wrong, they still had fun, but they said Carnival lacked in many areas that the other lines really excel in.

Also, we didn't feel crowded AT ALL on the Voyager. It was truly amazing! The only time it was crowded was around the pool, so you do have to stake out a lawn chair kind of early if you want a good spot. (But there were always chairs available.)

We thought the entertainment was FAR, FAR superior on RCI than on both the other lines. (I'm talking about ALL the entertainmet, from poolside activities and games, daily activities, nightly entertainment, etc... Much, much better.

And, there is really no motion at all on the Voyager. (I am very prone to motion sickness, and didn't have any problems on this ship.)

I think it is wonderful that you want to do this for your parents. When I am not working, I spend much time doing freelance travel photography on cruise-ships and have been on 24 cruises (15 assignments and 9 pleasure). For my money, I highly recommend Royal Caribbean based on my experiences with them. For comparison, my other experiences have been with NCL, P&O, Princess, Holland America, and Cunard. But I cannot recommend Voyager of the Seas to anyone for their first cruise because this series (Voyager, Explorer, etc.) is not a ship experience. Instead, Voyager is a huge floating block that focuses everyone on interior & exterior activities instead of being at sea. It has many limitations including slower speed than Legend class, being very difficult to dock in high wind conditions, and a passenger load that can be as high as 3,900 with all uppers filled. Add another 1,200 for the crew. (the only vessel that belongs at sea with 5,000+ people is an aircraft carrier). Instead I would try Rhapsody Of The Seas, Enchantment OTS, Vision OTS, or Grandeur OTS. These ships usually carry 1900 to 2000 pax and have a 2400 maximum. They are very comfortable, can visit more places because of their speed of 25 miles per hour (if needed) and smaller size, have 25 feet below the waterline for stability, and are still quite large at 915 feet long by 106 feet (panamax) wide. A cruise on one of these four will offer a first-timer plenty of options without paying the additional cost for Voyager (they charge more because of the novelty). As for the idea of having a more refined experience elsewhere, it is true that Holland America, Celebrity, and Princess will offer a more refined experience. But first see if your parents like to cruise before spending the extra money on refinements. Lastly, I am in the same age bracket as your parents and RCL has always hit the mark when I sail with them (1994, 1997, 1999).