Tough call - I couldn't imagine going to Disney without my DSLR - but I also have a tiny P&S and a mirrorless APS-C camera that I can use for various purposes as second bodies or in place of the DSLR on occasion. I HAVE traveled to the parks with only a P&S, and with only the mirrorless camera...but the DSLR was sitting back in the room ready to go, and still came out to play during that trip - I was fine for that one day going without it, but I might have a hard time going for a whole trip without it!
The one camera that can come closest to replacing the DSLR is the mirrorless, since the image quality is identical - the only things I wouldn't have are the fast focus and huge telephoto range for Animal Kingdom. Last week I was up at Disney for just one day before a business trip, and I only brough the mirrorless for light traveling - had a great deal of fun and got some wonderful shots...but that was also only for Epcot and MK.
I'm assuming your long range zoom is an ultrazoom P&S camera - those will have great versatility at the Disney parks, and really the only thing you'd be missing with the smaller cameras is the low light/high ISO ability for dark ride type shots. Otherwise, you could do fine and get some great shots without the DSLR. It's more up to whether or not you think you could do it without going into withdrawal!
(BTW - I'm currently a 3-Sony user myself,with my A550 DSLR, NEX3 mirrorless, and TX1 ultracompact. I've been alternately an owner of Canon, Fuji, Sony, and Pentax cameras over the years, so no blind brand loyalty...but my current models meet all expectations).
