DJs not on the lineup will be playing the lawn, according to the official facebook. I guess that explains the DJ Gabe Real self-confirmation, and IIRC, Franki Chan tweeted a couple months ago that he was going to be on the cruise.
This cruise is the perfect opportunity for some of these live acts to afterparty-style DJ sets in one of the night clubs or the lawn, so maybe that's part of it as well?
DJs gabe real, juice, jimbo jenkins, art, a special guest, and "primavera djs." Har Mar Superstar is also onboard for some reason.