Think of it as eight separate regionals that are happening all at the same time in the same building. There will be eight playing fields on the dome floor. You will be assigned to one of them. This will determine which sections of the stands your team will sit in, and which general area in the pits you will find your particular pit.
The implication of this is that there will be a LOT of walking! Expect the walk from your pit to queue your robot on your field to take 10 minutes. And they won't be announcing your queuing over the PA (that would just be insane) so you need to know your schedule and keep watching the clock so you know when to get going.
In addition to eight separate FRC regionals in the stadium there is a whole other building attached, and there's stuff going on there too. FLL will be happening in another giant room. There will be a schedule of seminars and workshops that will be available to your team with topics of interest to both students and mentors. These seminars go on throughout the day and they do overlap with practice times, qualification rounds, etc. so you will need to decide who can go to what and who will have to miss the seminars (e.g. probably drive team and pit crew). If Karthik is doing another talk on strategic robot design, I highly highly highly recommend you sit in on it.
In addition to all that, there's even more stuff going on outside the building! In another building down the street they have Scholarship Row which includes exhibitors from companies and colleges/universities vying for your attention. Go check that out when you have time. Great to meet contacts from different schools and companies and they hand out lots of fun free stuff too
In addition to THAT, there's an FTC tournament happening at Union Station which is a considerable walk, or a 10-minute shuttle bus ride, from the dome. It's harder to schedule time to go see this but if you have time and opportunity, go check it out.
You'll only need to scout for your division, and there could be 70-80 teams on the division. When students aren't scouting or watching matches, they can walk over to another field and see other robots playing, or walk over to the seminars, wander through the pits of your division or any of the other divisions, wander outside to one of the other buildings, wander over to any of the many concession stands, merchandise stands, etc. - there is so much wandering around they can do! Plan to allow them to explore, but definitely travel in groups so you people don't get lost alone.
Basically - plan to do a LOT of walking. Expect it to take 10 minutes to walk from anywhere to anywhere (from pit to field, from entrance to stands, from stands to seminar room, etc.) It would be very helpful for your mentors, and hopefully students, to have a texting plan that works in the States so you can signal to each other. Even then, be aware that cell service is spotty inside a giant concrete building. There's limited WiFi but don't expect it to work very well. Getting a student in the stands (such as a programmer) to go down to the pit is a bit more of a logistical exercise than it would be in North Bay. Find ways to allow groups of students to explore when they're not scouting or in the pit so they can take in other aspects of the event including going to workshops and exploring Scholarship Row, or going to buy FIRST merchandise. Expect big line ups and crowds pretty much everywhere. It's crazy, but it's so much fun.
When it comes time to gather for the big events - like opening ceremonies, or getting seating for the finals after everyone moves over to Einstein - get up and move FAST and TOGETHER if you expect your entire group to sit in the same area.
(Man, now I really wish I could go again.)