Hi, Gregory! There are quite a few options available to have some grown up fun during your visit to Walt Disney World. Depending on what type of entertainment you're looking for, You might enjoy some of these options:
JellyRolls - This dueling piano bar is awesome fun for the over 21 set. You will be amazed and astounded at how great they are at responding to requests and mimicking some of your favorite artists.
Atlantic Dance Hall - You can dance the night away to the most popular tunes from the 80s and 90s at this Boardwalk location. This over 21 location is just beautiful, and an awesome way to spend an evening.
Downtown Disney - If the night club scene is not your thing, you can find lots to do at Downtown Disney! From restaurants with live music (Raglan Road and Paradiso 37) to dinner and a movie - TOGETHER at the AMC theater, or even a few rounds of bowling (and sushi) at Splitsville Luxury Lanes, there is something for just about everyone. You can take in the show La Nouba by Cirque du Soleil or catch a band at the House of Blues.
My husband and I also love just walking around EPCOT in the evening without the kids. We'll make a dinner reservation, catch some of the shows, and enjoy a few cocktails as we wander around World Showcase.
Enjoy a wonderful, kid free evening!