Take both lenses to Orlando with you, but for most of the parks just take the 18-55 and leave the longer lens locked in your room safe. Take the longer lens to Animal Kingdom and use it on Kilamanjaro Safari to get pics of the animals.
Since you're new to photography, stick to the basics and keep it simple at first. Carry no extra lenses, but always carry extra memory cards and, if you have one, an extra battery. Don't bother to shoot raw at this point; just shoot jpg and look over your pics when you get the chance. Don't bother to look at every pic on the camera - that just sucks away battery life - instead, shoot as if you're shooting film and review your pics after you get back to your room at night. This forces you to concentrate on framing the shot in the viewfinder, and you don't waste time or miss follow-up shots by constantly chimping.
But the most important thing in getting good pics is to actually look through the viewfinder. Many people simply point and shoot, then chimp, and wonder why their pics don't come out. Look before you shoot; take the extra few seconds to really look at the scene through the viewfinder before snapping the pic, and you won't need to look at the pic afterward.
I bought my first SLR, a 35mm Canon Rebel G, in 1999, just before my 8th WDW trip (first solo trip). I had only one lens, a Sigma 28-80 that gave me exactly the same zoom range as your 18-55 gives you, and I used that lens through my entire trip and got the best pics I had ever gotten.
If you use the 18-55 as a walkaround lens through your trip, you'll probably come home with some fantastic pics.
. I plan on enjoying the first trip but real excited about getting some nice pics. Being on the bottom of the learning curve, I know it will be a lot of auto shots and then when i have time waiting for attractions or the family to do other things I will play with all the settings and trash the bad ones later. LOL thank goodness for digital. 
