We didn't have problem with bags on most rides, you just have to hold on to them. Backpacks are must easier to use though. They are easier to carry and hold on to on rides. We always made sandwiches for lunch and had snacks and water in our bags when we went into the parks. The security people checking our bags didn't care, one even asked if he could have one of our sandwiches and we did offer it to him but he didn't take it. I am pretty sure an 18 month old can go on the rides in Fantasyland,s Mickey's and Minnie House in Toon Town and Donald's Boat in Toon Town, the Railroad, Magic Carpets of Aladdin, and if he/she isn't too scared the Haunted Mansion and the Jungle Cruise and most of the shows are good for little ones too and that's all in Magic Kingdom. At Epcot all I can think of is the new Nemo show and all the fish and maybe the Land, Imagination, but there are some dark scenes in that one, Innoventions, Universe of Energy, and there's little things to do at the end of Imagination, and there is a littlel playground type thing at the end of Misson Space. In World Showcase there are little Kidcot spots, both children can make masks, well thats what they had last time that I was there, and at each country there is a little thing that the cast member puts on the mask and a stamp and maybe their name in the language of the country. At MGM there are all the shows, The Great Movie Ride, but there are some scary scenes in that, PlayHouse Disney and Honey I Shrunk the Kids Playground. At Animal Kingdom, there are all the shows, and if he/she can walk the Lion King Show might have him/her help out with certain parts, and of course all the animals to look at. I saw the last time I was down in Disney that parents gave little ones flashlights to have turned on in the dark on rides or shows when they are scared. I hope this helps. I have been there a lot and I can only come up with those for you. There are also all the Characters and Parades to see too. I hope you have fun.
My big thing that I am trying to figure out now is what to take for a bag----can you carry purses/diaper bag on the rides with you, or do they have to be attached to you like a fanny pack or backpack. Can I carry outside food/drinks into the park. Are there many rides the 18 month old will be able to do?? Answers to these questions and any more tips would be so greatly appreciated. Thanks
