Take a walk on the wild side...and party down at the Louisville Zoo with their extended hours this June and July. The Family Twilight Hours run Thursdays through Saturdays until 7 pm (families must exit the zoo by 8 pm or risk spending a night with the lions).
Family Twilight Hours also includes discounts and ride privileges for zoo members after 6 pm. Members will get free carousel rides, 10% off of the gift shop on Thursdays (maybe then you can get your kid a stuffed animal for only $30) and use of Zootram Shuttle on Fridays. No mention of the train.
I'm a big fan on the zoo, and it's not too late to become a member. If you plan on going more than a few times this summer, the membership virtually pays for itself. For more information about the summer hours, or to become a member go to louisvillezoo.org