I have a few thoughts ..... (yes, I'm known as a "mean mom" to my kid's friends, and that's A-OK with me!!).....
-There is no way on this earth that I would be taking them to WDW (or anywhere else) until their behavior changes radically and for a prolonged period of time (at least 12 months). IMO, they haven't earned the priviledge to be taken anywhere.
-Do NOT put them on time out in their room! Find a boring corner to sit them in, a landing on a stairwell, a chair facing the front door...make it as boring as possible, and do NOT talk to them during it, no matter what they're saying to you.
-My kids have known from about the age of three that anything they leave lying around the house (toys, clothes, art supplies, whatever) goes into a Hefty bag and donated to GoodWill. At first I had large tax deductions as a result, but they learned quick! (This was the rule when I was growing up too; with 12 kids, I think it was the only way my mom could keep the house presentable).
-If they misbehave, I'd make them wear signs around their necks. Again, my parents did this when I was growing up. Wearing a sign that says "I'm childish and I whine" tends to stop that behavior rather rapidly. (Yes, if it's an issue before a ball game or the walk, I'd make them wear the sign to that).
Personally, I would have hunkered down in the house with them for the weekend and cancelled the plans; their first committment is to the family team, not baseball or to the walk, even with sponsors. Again...I'm mean.
We volunteer as a family two nights a month at a meal program downtown for the homeless. I think there's nothing like helping others less fortunate to open kids' eyes to how truly rich they are, and I think it's a huge reason why neither of my kids have ever done the "I want...." or "Can I have........" whine.
I will tell you that I have two of the best mannered, best behaved kids I know. DS18 is LOVED by his teachers; I constantly hear he's wise beyond his years, and how polite each of them are. Our house is peaceful, fun, organized...and the friends who think I'm "mean mom" seem to always be hanging around....lol.
My sister's kids are totally spoiled (they're 15 and 17). Last month my sister got so fed up with them and their behavior that she stripped their rooms of EVERYTHING (they had a blanket and a pillow each for nighttime). Day by day they've had to earn back a piece of clothing, their beds, makeup, hair stuff, etc. It's going to take a veryyyyy long time for each of them to earn everything back. So far they're still behaving 100% better than before.
Nip it in the bud now.......you want this behavior to be a distant memory when they hit their teen years! Good luck to you!