Disykat - thanks for your input.... I definitely would NOT demand that they let me take her, but I don't believe you fully understand the dynamics of my family. We are VERY VERY close, which is why I even entertained the thought of just giving it to her. This is in NO way even remotely associated with sabotage..... it makes me laugh to even put the word on paper (or screen, as the case may be), and sad that you even thought it. I spend A LOT of time with all five of my nieces.... I pick them up on a Friday night just to do something fun, at which point my brother(s) usually wink with gratitude and go have their own "fun". I have done more than my share of "helping" to raise them, and not that anyone is counting, but they have saved probably literally thousands by dialing my number when they wanted to go out. I only say all of this to give you a taste of the dynamics of my family.... this is not, in my opinion, at all "out of line."
Keli - that's an excellent idea. There will be no problem with my DB, possibly just his wife (and the basketball thing), and there will be absolutely NO problem what-so-ever with my other brother and his wife.... they are much more laid back..... they will think this is super. So, maybe, considering the offer will move from Britt to Sadie (one of the other family), should they decline, they will see the value in it. And yes mamajoan, if I "ask" them first, I will reveal the entire plan to them all....... in fact, I would have anyway whatever time I "revealed" the gift, as I would NEED to explain to my other "peanuts" that their turn would come in due time.
Please understand me when I say that I decided on this because I would love to spend 7 days just hanging out with my nieces (each with their own interests) on the Disney Magic.... it's purely because I love them, they are my life, I have no kids of my own to experience this with, and I wanted to experience it with them. I could take them all at once for less money, but to have each one individually and spend the time doing only what they as an individual likes, just makes me soooo excited. Britt (13) will love the spa... and I can't wait to get a manicure and facial with her. Sadie (11) will love the game room, game shows, competitions, and as I am just like her, I can't WAIT!! Callie (10) will LOVE the ocean, snorkeling, stingrays, dolphins.... she wants to be a dolphin trainer, you know.

Kendra (7) will just LOVE the people, the waiters, the host/hostess, the other kids.... people, people, people. And Chloe (3)... well, she's just my buddy, and if I'm going, she'll love it.... BUT Goofy and Mickey will be there too... BONUS!!!! Anyway, I think you see that this is more for me and the time I get with them.... I'm not out to sabotage or create ANY issues.... which is why I asked the question in the first place.