It's huge. Plan for a lot of walking.
I agree with the PP who said buy the ticket for everything; they tend to nickel and dime you with $1, $2, or $3 add-ons throughout the zoo. The bug carousel is $1 and the Butterfly Garden is $2 and the Congo is $3 and the Children's Zoo is $3...etc...(on top of base admission)
Make sure you go see the lions. Yesterday the cub was out and playing with the mom, and the dad was roaring.
Make a plan in case you get separated from your kids, similar to what you would do in WDW. It was free day yesterday, but insanely crowded and a LOT of kids will be there on field trips at this time of year.
I think it's supposed to be sunny tomorrow...wear sun block because there is not a lot of shade on the walking paths around the park. I think it's also supposed to be 70 or 80 degrees so dress for that also; you don't want to be uncomfortable.
You can PM me if you want for specific directions or anything. The traffic around the zoo can be a nightmare, particularly at 5pm on a Friday.