What a great rate at the JW. I'd snag it.

Two other points to add:

I went to Orlando a year ago with a friend, her two kids and her parents. We stayed at the RI at Sea World and actually found it very easy to get back and forth to the parks and the hotel was great about upgrading us ahead of time so that we were able to stay in one, albiet very croweded, room. Their breakfast was a step above the usual RI fare and set-up.

Also, I understand the Marriott loyalty, but nothing can beat staying at one of the Disney Resorts, especially if you have kids. The Grand Floridian, Beach Club Resort, BoardWalk Inn, Yacht Club, Contemporary (which isn't anymore), Polynesian and Wilderness Adventure are such great hotels, with kid friendly activities at every turn, and it's so easy to go back to the room a couple times during the day for an hour's break and/or to drop of the crap you somehow acquire as you walk the parks. The Disney Resort rooms are family friendly, too, in that a family of five will be able to stay in a single room.

Have fun!