Team 461 has a simple system on who goes to the comp:
1) The Pit Crew
Like said above, this is a small core group. It should include a couple mentors, your drive team, and a few other students. I think ours generally comes out as 10 people. They leave Wednesday night or Thusrday Morning of competition and the rest of the team, which isn't needed at that time technically, comes the Friday of competition.
It is important to choose your crews carefully.
2) General people
Encourage as many as you can to go, but if you're travellin to Atlanta from somewhere up north and it involves plane tickets, be sure to sort everything out ahead of time. At your home regional? Have at it!
. Be sure to respect the decision of the venue.