You shouldn't have to. I can't remember the exact cut off number, but 7 people were no problem for the one room executive we have booked for June, we ended up with 5 people. I believe that it was over 10 people if you got a 2 bedroom executive suite.
It's really hard too say what kind of rates you could end up with, so your best bet is to check regularly, because prices can very from day to day, hour to hour or person to person. On our first visit to the Dolphin, June 2011, we ended up getting an a 1 BR executive suite for an incredible price of $309 a night, but it took about 6-8 calls over a few week period to get that price. We initially booked our executive suite for June of this year for $399, but after a few call we got it for just under $370, can't remember the exact price. I was quoted $359 on one call, but when my brother tried to book it a few hours later that price wasn't available.