Young 2 or older 2? Girl or boy? Have a zoo they go to at home? Any idea whether they will like characters or are scared of them? My DD did not like AK at all at age 2. She spent the whole time there begging to go back to MK or EPCOT. There was no Princess presence at AK.
She was a character fanatic, so her favorite park other than MK was by far EPCOT-- so many characters to meet. She loved the boat ride in Mexico, Living with the Land, Nemo, Turtle Talk with Crush, the Kidcot stations in World Showcase, the entertainment in World Showcase, and other things too.
With a 2 year old though, I would consider just spending the 2 days at MK, especially if they like the characters and you spend time doing that. Toddlers can really slow you down at WDW- they need time to stop and smell the flowers. It is fun to see what little detail at WDW you have not paid attention too for a while that suddenly becomes the most interesting amazing thing to them. DD is 11 now, and her two year old trip (which was her first trip) is one of my absolute favorite WDW trips. You might want to do MK the first day, and then make the decision as to whether to do a different park, or just spend the 2nd day at MK.