I looked at your profile to see what you have for equipment. You have the ideal lens for the job, the 18-55mm zoom. The first time I shot with a DSLR at WDW, I had the XSi, the 18-55, and the 55-250. Whenever I used the longer zoom, I was always at the 55mm end.
The 24-105 is an excellent lens, and is an ideal walk-around lens on a full frame camera. It would likely be good on a crop, but as was suggested by Motor On, the 24 on a crop isn't very wide. If you're shooting a crowd of people, wider is better. Also, as a self-proclaimed "newbie", spending the money on a pro lens is apt to disappoint. I know people who use very high end equipment who produce garbage.
Your profile says you're in Tacoma. Take a day (or two or three) and walk around the city. Discover it or rediscover it from behind the camera. Take a family member or 15 and experiment. What works? What doesn't work? That's where you'll make your investment.
WDW is great. Have a fun time!