First of all Don't Be Scared!!!! Cruising is easy and painless (except on the wallet!!) You get on the ship, unpack your bags, go places, get off of the ship, get on the ship, eat wonderful meals, experience magical entertainment, relax and then finally pack up your bags and leave the ship (ok this last part about leaving is the HARDEST part of cruising!!!)
No one gave the other obvious online resources so here it goes...
Here is a list of links to
DCL resources
DCL Official Site
Dave's DCL Tribute (be sure check out the "External Links" section for more resources

ie Cast A Way Club

)
Magical Disney Cruise Guide (see links on the left) The Magical
Disney Cruise Guide is HUGE document about all things related to a DCL cruise
There is a book called the
"Passporter" for DCL that has lots and lots of information about cruising with Disney.
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Time of year to go. Since your son is in elementry school, you pretty much can go whenever
you want. We were paranoid about pulling our kids out for a weeks vacation - but it turned out to be absolutly no problem. Not too much of an issue in middle school, and there is almost no way I would pull the kids out of high school.
Easter, spring break and summer vacation, christmas / new years are the most expensive times of the year to go. Huricanne season is from June to November (but most activity is in the August to October time frame). Sept / Oct. are some of the least expensive times to go. December / January are a bit cooler (the water too) than the rest of the year, August is Dang Hot and Humid. If you are going to do a 7 night eastern then the weather isn't much of an issue during the winter months - St. Maarten and St. Thomas are pretty nice and you will notice the Bahamas are cooler. 7 night western doesn't go as far south as the eastern so the daytime temps might be an issue for you.
Length / Type of Cruise:Disney offers serveral different cruises: 3 and 4 night Bahamas, 7 night eastern caribbean, 7 night western caribbean and a 10 Caribbean holiday cruise again in 2006. They also offer a "Package" Land/Sea cruise that give you 3 nights at WDW and 4 on the cruise OR 4 nights at WDW and 3 on the cruise.
the Bahama cruises stop in Nassau and
Castaway Cay (DCL's private island). The Eastern goes to St. Maarten, St. Thomas and Castaway Cay. The western goes to Key West, Grand Cayman, Cozumel and Castaway Cay.
Dinning and Entertainment:All meals are included in the price of the cruise (unless you and your significant other want to eat a dinner at Palo - the adults only dinning room - $10 per person fee for a fabulous meal!!) Soda is included at sit down meals, there is soda available at the drink station. Adult beverages, smoothies, speciality coffees carry an additional charge. For dinner you are assigned a dinning rotation (which dinning room you go to each night), a table number and wait staff. You sit at the same table number for the duration of the cruise (for dinners). Your tablemates and wait staff stay with you throughout the cruise. For breakfast and lunches you have the choice of a sit down or buffet meal.
There is lots of entertainment provided for your enjoyment. Nightly there are shows in the main theater (Walt Disney Theater). These are mostly Broadway class productions. There are other, smaller events available in other locations.
Kids Clubs:There is a club for kids to go to during the day and night (like 8am to 1am). There are actually two clubs: one for 3-7 and another for 8 to 12yo (I think that's the age breakouts). Most kids love these and don't want to leave. Some do not. DCL has a lot of great people working with the children. Really no issues here. There is a third club called the Stack (or Aloft depending upon the ship) for 13 to 17yo.
The last thing that I'll leave you with is the issue of
gratuities. DCL and most cruise lines say that the cost is the cost of your cruise. What they don't tell you is that they don't pay their wait staff and room stewards squat. We are expected to "pick up their salaries" in the way of gratuities (tips). When you "do the math" your first reaction is "dang, that's a lot of money!!" But when you think about it, it's pretty inexpensive for the amout of service that you are receiving and how much that they want you to have an excellent experience. The total cost for gratuities based on the current guidlines is about $11 / night / guest. So for 3 people (yes the children do count) the "published guidlines" for 3 nights is $97.47, 4 nights: $131.25 and 7 nights is $228.75.