Get the permit, call Pro, done. It's a year ahead so I wouldn't depress yourself planning too much until you get the permit! You'll have plenty of time to figure it out.
I always like big groups, trips are a lot of work, everyone has days where they don't feel great, many hands make light work. Make the most of living communally for a couple weeks.
We always do a morning meeting at the boats before we shove off. Plan for the day, camp issues, groover report, anything to mention.
We do this by family on normal trips but for the Grand we did a bandanna draw the night before. Your color was your team for the trip. Cook crew, cleanup crew, groover, day off. Everybody always knows what they are doing. Rotation is always from dinner through lunch the next day.
Biggest thing should really just be figuring out the itinerary and what you want to stop and do and see with the time you have down there. Everything is a little trade off but it will all be good! Just awesome being down there.