Even with the D800, you'll want a prime lens for dark rides...
I've done both, full dSLR and point and shoot (the RX100). They are very very different experiences. When I carry the dSLR, I'm focused on capturing great photographs. When I carry the smaller camera, I'm more focused on my family and the moment, with the ability to capture some photographs on the side. Not saying I ignore my family when carrying the big camera, it's just a different emphasis of my perspective.
When I'm someplace where I really know I'll want to capture great images, I'll carry the big camera most of the time. It's worth the extra weight, to get the best potential out of the camera. That said, if I know I'm running around for hours and hours on the go, that's where the weight of a dSLR, especially a big one like the D800 with 24-70, can start to slow me down after a few hours.
So I'd think carefully..... If I'm going to be on the go for 8-10 hours straight with few real breaks, it might favor taking point and shoot instead. If I'm often going to have my "hands full," it's another reason to favor the P&S. If I'm going on a lot of water rides and concerned about protecting the camera, etc... easier to stick a P&S in my pocket or in a plastic bag.
On the other hand, if I'm going to the parks for a couple hours in the evening, or a morning mostly of character meets, or low impact like just a couple hours around Fantasyland, then I'm much more likely to carry the big camera.
My best advice would be to bring both cameras on the trip. Depending on the day's itinerary, I'd decide which camera to leave in the hotel. A morning of dark ride shooting? Bring the D800 with a prime lens. Night time landscapes? Bring the D800 with the 24-70. A day of commando running around the parks doing every possible ride? Bring the point and shoot.