We did this a few years ago. It's a fairly long show. If I remember correctly, it's at least 2 hours you are in there. Going early also gets you a photo op with Chip, Dale & Goofy (at least when we did it). Not everyone gets that as they leave once the crowd gets large and they start letting everyone in.
Figure it's about an hour or so to eat & dance w/ the characters, they put on a cowboy show and then dessert and more dancing with the characters. It's not quick as there is a show involved unlike straight character meals where you can kind of get in and out depending on how fast you eat and how the characters rotate.
The characters do not visit your tables here. You must get up and initiate contact with them.