When we were there in June, the greeting was at a special time after the lounge closed. They reopen it for the meet-and-greet exclusively for the guests who have the MMB add-on.
We got there a few minutes before opening time and got nervous because nobody was around and the cast members in the shop had no idea when I asked them about it, but right at the scheduled time, a host came down from upstairs and checked us in. We stayed about 30 minutes and only had 1 or 2 other groups show up during that time.
The characters don't provide autographs, but we were given a signed postcard with their signatures instead, and there was a Photopass photographer with Nick and Judy to capture the photos.