I just found it on the
Disney cruise line blog's site. It's listed on Day 6, 4/13/18, Panama canal day. (It's on the second page, under Character Appearances)
http://disneycruiselineblog.com/wp-...nder-14N-WBPC-Day-6-Panama-Canal-20180413.pdf
"Tiana's Steamboat Supper Club" "Adults head on down the bayou, as we get into the 'spirit' of the night, with great live music, dancing, and even a little magic. Please visit the guest services desk, deck 3 midship, for booking. (18+, limited availability, nominal fee.)"
I have a feeling that this is probably going to be limited to the longer cruises, like the Panama Canal or Transatlantic...but who knows...