When my DDs were 2 they liked:
The Living Seas (they could've spent all day in there)
Spaceship Earth
El Rio Del Tiempo
The marketplace in the Mexico pavillion
Jouney into your Imagination
if you are going when it is warm: playing in the fountain (bring a change of clothes for this)
Play area in Mission Space
Believe it or not, my kids loved looking in the shops in the World Showcase.
The great thing about 2-year-olds is that they are so easy to keep entertained (at least mine always were). While my older kids are riding Test Track or Mission Space, my 2-year-old was perfectly happy to just stroll around the park and look at the merchandise in the kiosks, the beautiful gardens, the bunnies or birds that may be in the area. Of course, the old standby was always El Rio Del Tiempo...I think we must've ridden that at least 20 times on our last trip.