Ds teacher goes through this every year. She plans the senior class trip for a group of that size too. She usually calls the group dining and sometimes the restraunt manager themselves.
1. As the other poster said, you will most likely have tables split up and also maybe a staggered time, like 10-15 minutes apart.
2. Most likely you will not get the "prime" time of the meal you want, you likely could get the earliest or later seatings etc. I know this past year around May 21 she booked Tusker House Breakfast and Whispering Canyon Dinner. I think the breakfast was around 10:30 am.
Best of luck and have a great trip.