Generally, cruise meet threads get active somewhere in the 3-9 month window. Although, if you have several in the group who are really into it, a thread can be very active from the start. My first cruise meet group was already 10-15 pages into it when we booked the cruise (at 18 months out). Other groups didn't really get rolling until much closer.
Just depends on how much those in your group want the group to succeed.
If you want a FE group, and there's none going on your cruise meet thread, you could step up and maintain the list. Basically that's all you need to do. Keep the list and make sure everyone gets a copy of it. You can do that via Conversations (PM) or emails, if people want to give them to you.