Hello, Maria,
I have great news for you; the water play area, called Casey Jr., in the Storybook Circus area of the new Fantasyland area at the Magic Kingdom just opened!! In fact, you can read about it at the
Disney Parks Blog. In addition to this, the newly renovated Dumbo is up and running; and the second half of it the ride with its
interactive queue area is scheduled to open in July. While I don't have the specific dates, I'm sending you a big dose of pixie dust that the opening will officially happen prior to your trip. In fact, when were at WDW last week, the Big Top had quietly opened for some guests to experience for a short period of time.
As for the rest of the Fantasyland expansion, it is ongoing through 2013.
By the way, my teenage sons wanted nothing to do with the new Dumbo until they saw it at night. To quote my 15 year old, "Wow, that looks great." I think when Disney can impress a slightly-jaded teenager, they've done a great job.
Wishing you a wonderful trip!