J.B.
We were just there a couple of weeks ago with our daughter who is 2 (35 months).
I would avoid the ducks...the steep hil and drop into the water can be pretty scary for a child.
Timbavati is great. Lots of animals to see...lots of nooks and crannies to explore. Worth the time and worth the money.
Riverside and Great Northern Railway is AWESOME. We've done it two years in a row. My daughter LOVES it...fun little train ride and a great gift shop for Thomas fans.
WI Deer park is really fun. The Deer can kind of get in your face so if he is at all sensitive you may want to be sure to bring in your stroller so that he has a safe place.
Main street is fun to wander...make sure you check out Rail Dog for lunch (just off of the main street). Great food...awesome fries...the guy who runs it is really a character.
Buffalo Phils. AWESOME food. Eat in the Train Room and a train will deliver your food. Knuckleheads is an indoor amusement center and is attached to Buffalo Phils. If your little guy likes bright games and lights this place would be great.
Have fun! Any other questions just let me know...we go to the Dell a LOT in the summer since we only live about an hour away. (In fact, we are going tomorrow..lol!!!).