Cabin grats are $18/day per person and can be paid at the time of booking via the web site.
Prices in the planner (inc drink package) are dynamic - you can get a feel for them via the web tool hack in this thread:
A few months ago and from reporting here on CC. Somone could tell you that there was no enforcement on this weeks' sailing and there could be on yours. Again, go with the overall reporting trend.
You'll need to arrange that.
Any competent RCI specialist TA would work for your reunion.
Cabin pricing is dynamic - the main perk for such a big group is a discount (of one basic fare) for any multiples of 8 cabins you book.
The ship just started sailing about a month ago and the number of CC posters who've sailed in such a cabin is probably quite low. The few posters who may have firsthand info also may not frequent CC that often.
Tendering at Coco Cay is not really feasible anymore. The dock and infrastructure for tendering was all removed when they put the pier in. Kind doubt they would tender onto the beach.
Some of the info for Indy is also true on the rest of the Freedom class so looking at those can also glean some info.
Biker, who is enjoying thread resurrection day.