We have been on two Disney Cruises and are getting ready to go on our third next week. It is amazing, magical, amazing, and yes you should do it! :) We've been on most of the major cruise lines and Disney is my personal favorite, even as an adult.
I don't necessarily drink the Disney Kool-aid, but I can't recommend these cruises enough. We have only been to DW for one day because my husband is sorta Scrooge-y about it and really doesn't want to go because of the lines, crowds, etc., but the cruises on the other hand are amazing and everything you want/need.
It has the plusses of the Disney brand like characters, branding, awesome shows and incredible service but not all the fuss of waiting in line and dealing with cranky kids.
The kids club is beyond amazing. My kids LOVED it and wanted to be there a lot. They open early and are open late so there is plenty of opportunity to have grown-up time and do what you want. There are adult only sections of the ship as well so that's nice if you want some quiet time at the pool, etc. The food is very good and they are very conscious of what kids like/want, food allergies, etc. Besides the pools, splash parks and various other things on board, there is a movie theatre that plays current Disney movies.
There are some add-ons once on board, but not a ton, especially if you're prepared for them. The most annoying add-on (I think) is the popcorn they sell for the nightly shows and movies. You can get a reusable tub and refill it for a better price each night, but it's annoying. You can bring your own snacks but that is also kind of annoying. They have smoothies and shakes and stuff at the restaurants that are on add-on sometimes but I don't find it hard to avoid those because there are so many great options that are included. I will also say that Disney Cruise excursion prices are the highest I've ever seen on any line. They are super expensive. It's very easy, however, to do your own excursion for a fraction of the price. One of the other big add-ons is the Bippity Boppity Boutique. Both my son and daughter go to it and they both love it. We don't do the dress option for my daughter because she doesn't really like dress up clothes anymore but still enjoys the hair part. If you were going to do a dress I would bring one from home. They are the same dresses you find in the store but way more money. If you bring one they are fine with it and will dress them in the boutique. Without the dress, I find the boutique very reasonably priced.
Finally I will say that we have gotten both are cruises for very good prices. If you kind of stalk the disneycruise website you can find deals about 2-3 months before you sail. We always do the "guaranteed verandah" room and have had no problems. This option gives you a much better price but doesn't allow you to choose your room. We haven't had any issues and always get great rooms with great balconies that are near the pool.
I know this post is forever long but seriously you should go. My kids are 7/9 and are still so very excited for this trip. And the amazing part is...my husband and I are equally excited too!