Roy's is pretty expensive. Probably not the best pick for this group of cheap bastards (and no, I'm not including myself--when I'm on vacation, I don't care about prices--I paid like $20 for a friggin pancake in Orlando!)... But the Garden Walk offers other possibilities... I would never say no to the Cheesecake Factory, but I sense they won't have the seating for a big group. My local one definitely does not...
I also don't recommend the one a mile away. We should keep it walking distance, so people can come and go when they want, without having to worry about getting a ride...
Roys just showed up in the title, I was trying to show all the options at Garden Walk. That Cheesecake Factory is good sized. I have met some friends there before and they had a group of probably at least 20.
Also if the convention has buses to an from hotels there are a number of hotels right next to it. I am not trying to say its the best option I just know they are well suited to handle a larger party. It may not even be a mile depending on where the enterance and exit to the convention really is. I haven't been there since HS.