For a 2 year old pretty much any dark ride or character meet & greet is good (if he/she isn't afraid of the characters):
MK: Pooh, Ariel, Peter Pan, Small World and of the character meets
Epcot: Turtle Talk / Living Seas / Imagination (Character Spot) (frankly - may be a waste of FP at Epcot if you're going to another park that day)
DHS: Again very few FP worth it here that you wouldn't be able to get in without them: Little Mermaid / Disney Junior / Frozen Sing Along
Animal Kingdom: Safari / new Pandora River Journey / Nemo & Lion King Shows.
In general - FP will be of great use in MK and AK. Unless you're at a peak season, they'll be of more limited use in Epcot and DHS. If you have more than one adult, remember you can get a couple FP for yourself and use rider swap to ride some adult rides. (If you do that - have one adult get a FP for one adult ride, the other get a FP for a 2nd adult ride and then use the other two passes for the kids rides. (And as someone else noted - you're not technically get a FP for the 2 year old since he/she doesn't have a ticket but I assume you mean what FP the adults should get to take the 2 year on).