Sounds wonderful! With friends and family, it will indeed be magical! 7 days is the way to go... we wouldn't go for any shorter. Our kids were 9 and 13.... and they beg to go back again on a Disney Cruise. Our server at our meals was from Slovakia, and he was the BEST! Our kids still talk about "Thomas" from the cruise... he treated us like we were the only ones on the ship! It's things like that, the servers, the little touches that Disney has that make it so magical.
I think this may be the last time we can get down to Disney with my daughter (she will be a sophmore in high school in the fall when we go) but our kids love Disney so much that it may not be the last! Last night she told me she wants to get married in Disney World, or at least honeymoon there! I hope she finds some one who feels the same way! I could handle that!