you guys are going to have a GREAT time, and if you can see it all in a week with 2 little ones, you aren't "seeing" it the right way!
we're on trip #8 with our 3 because it is SO MUCH FUN to explore and experience with them...the majority of our time WASN'T spent on rides at 2 and 3. here is a cut and paste of mine from a previous post (the poster was asking about her schedule with her preschooler):
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the other great thing about your plan is that you have SO much built in time to explore and play. your daughter's age is perfect for really soaking up the magic and it is SO easy for kids to find their own joy...as so many others in this post and others have mentioned, the fun of taking preschoolers is seeing what makes THEM happy (and so often, it is not the rides!)...it's the monorail rides, and finding jewels imbedded in the cement (in the oasis at AK and near magic carpets in MK), and seeing the fiber optic lights in the cement and light posts in epcot (near innoventions), and watching the staged show in front of the castle, and trying on silly hats in stores, and chasing lizards (at the resorts), and pooh's playground in fantasyland, and trying to catch the jumping fountains (near the imagination pavillion in epcot), and watching the kids dance to music they recognize, and seeing their faces light up when they see Mickey Mouse, etc etc.
i don't recall seeing world showcase on your to do list in epcot. some of the exhibits were fine for my kids at 3.5 yo, but i found that my kids LOVE exploring back there....dancing to the bands, watching the model train next to germany, running in the garden maze in UK, finding fun architecture in norway, learning how to say "hi" in different languages from CMs, everything in the mexican pavillion (and now they have the new ride there with the donald duck/3 caballeros), finding fountains in italy/france/morocco, poking in and out of shops, running up and down the steps (when empty, of course) in italy, etc. we also like to walk "around the world" and get desserts from a bunch of different countries. there are also the kidcot stations where kids can color/collect masks, but i use those as a "last resort"..they use permenant markers and my kids get plenty of coloring time at home!!
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have a great time,