The Seneca Park Zoo has come a long way from my first visit 10 years ago, but for a city of this size, it need to be larger. Don't get me wrong, it's a good zoo, with lots of nice exhibits, but compared to Erie (PA) it seems very small.
The Zoo does a great job of getting in "touring" exhibits, such as the black bears (which if you haven't seen, go check them out - they are pretty cool) and the warthogs (from last year). Their newest exhibit with the Mountain lions, seems to be catered to the kids with the new "up close and personal" viewing area they have (they now have a periscope kind of thing working for them).
Your best bet, if you plan on going more then once, is to buy the family membership, since after two visits, it is paid for. The member ship allows you to be invited to a lot of "members only" type of events.