I have never gotten it together to do a trip report, but have taken toddlers to the parks on 3 trips and am happy to answer questions! We took our older DD when she had just turned 2 (in 2011), in 2014 our girls were 5 years old and 16 months old, and last year they were 6 years old and 27 months old.
Both of our girls LOVED the characters when they were 2+, but at 16 months our younger DD wouldn't go near them until the very last day she interacted with Stitch at 'Ohana while my DW was holding her.
As far as a 2nd park choice, choose the one that appeals to you & your DH most. EPCOT has the most attractions that a toddler can do, but there are good points about the others as well. AK was probably my toddlers' least favorite, but if your son loves looking at animals he will have a good time there.