How wide is wide enough for a disney trip? im not positive what parks we'll be visiting and so on, but i know i will be needing a wide angle lens for all the great architecture and also for taking pictures of my family in close proximity. i was thinking of the tamron 17-50 f/2.8 (or the tokina 16-50 f/2.8 if they ever release it). i have a 50 f/1.8 for indoors/low light photos and a 70-210 f/4 for the animal kingdom if we venture out that way. but would a 16 or 17-50 be wide enough for disney? ive read posts from people saying a 10-20 or 12-24 was great and others saying they would never go to disney without a 18-200. any suggestions from those that have been there? im also going to las vegas a month after my disney trip, so i figure i will be able to use the same lens for the same type of photos. any help??