We actually did this for our Feb. 2011 trip (we suprised them Christmas 2010). We got them the little t-shirts that say "I'm going to the Walt Disney World resort". We held those for last. We actually videotaped it which was great because our oldest DD was really starting to read well at that point and we had her read the shirt, which she did...no reaction...then I said "what does it say???" she said "I'm going to WDW...", and I said..."and that shirt is for you???"....she said "yes", and I said..."so what does that mean???"...meanwhile, little DD is just looking at the shirt clueless when all of a sudden our oldest put 2+2 together and starts screaming and jumping up and down shouting, "We're going to Disney!!!" I love watching that video!