I vote a 5D or 7D and a 24-105. Put a black rapid strap on it and go. Keep it to 1 Lens. Then just bring a cheap 20$ sling and throw a speed light in there, a cloth, and a Joby. The sling will also double as the family 'stuff' sack and keep you from holding onto souvenir bags. WDW has so many places to sit a Tripod it's ridiculous, so you won't lack for railings or trash cans to stabilize. With one lens I found this approach just as rewarding as going with a P&S. Long exposures were sharp, the range made shots easy to compose, never felt that 'I wish I had brought my ....' Feeling.