we just got back with our three 3.5 y.os...MK is, of course, our favorite, but epcot is a close second, not because of the rides, but because of the experiences...it is so great to wander epcot with one (or 3!)this age...
the living seas is wonderful (and we didn't bother with turtle talk....line was LONG)
in future world, my kids do like the "living with the land ride" and although you mentioned that this won't apply to you, my kids just made the cut off this time for soarin', and they went on it 3 times and loved it!!! pretty amazing for kids who are afraid to ride the winnie the pooh ride, huh?!? .
we like the jumping fountains back by the imagination ride, and if you are going soon, there are a number of playground areas set up for the flower festival around the walkway to world showcase...
world showcase is the real gem for kids this age (which is why we go 1 morning for a few hours, but then make WS a pretty regular after-nap destination)...
every country has SO many little experiences for kids this age, including the kidcot stations (which we used as a diversion, when necessary, but not as a motivation---my kids could color with those stupid permanent (!!!!) markers for at least 30 mins. in each country if we encouraged it. we tried to downplay/avoid those if we didn't "need" them...we all had much more fun exploring everything else!! ).
each county usually has some music/show in the afternoons/evenings which are always interesting to our kids, even if only for 10-15 mins.
we usually ended up getting one or two food items each evening in different countries, which the kids really enjoyed.
mexico has "el rio del tiempo" ride, which my kids LOVE. they also like wandering around the stalls inside, looking at the art in the front of the bldg, and we usually eat outside 1 meal...nice to grab a table overlooking the lake and people/boat watch.
you can no longer get on the viking ship in norway, but still fun to look at. we haven't tried maelstrom with the kids (see previous "afraid of pooh ride" comment)
germany has a model train set up outside between it and italy (just for flower festival?). this was a huge hit with my kids.
italy has all of those steps/bridges to climb up/over near the water.
at the outpost, my kids liked playing on the drums
at japan (and UK), we liked wandering through the gardens
EVERYTHING in morocco is fun to explore (and my kids love "mo'rockin"..the band)
well, ok, you get the idea and i'm running out of time. we just really like wandering around back there (in and out of exhibits and stores, eating all sorts of foods, looking at the different architecture, walking around the lake, dancing to music, etc) and it is rarely feels super crowded because epcot is so big.
it sounds like you have just your DD? i would imagine it to be much more difficult to entertain older children while going at a preschooler's pace and with a preschooler's interests, but if you have that luxury...ENJOY it --it really is such a fun adventure!
have a great time,