Macaroni Grill is huge, but I've never once heard a good thing about its food. Seriously, think twice about recommending it.
Most of the restaurants along Denman are smallish hole in the wall type places - not places that can handle 300-400 delegates. Yaletown and Robson Street would probably be a better dining destination in that situation. I know you're not seeking a place that can handle all of them at once, but if you're going to make official recommendations, you'll probably want to make sure that they could handle 50+ businessmen (and ladies) arriving at once.
The only restaurants I can think of that might be appropriate within walking distance of the Coast Plaza:
The Boathouse (at English Bay)
http://www.boathouserestaurants.ca/
Milestones (at English Bay)
http://www.milestonesrestaurants.com/
Delilah's (underneath the Coast Plaza)
http://www.delilahs.ca/
Smaller restaurants worth looking into:
Raincity Grill (for local 100 mile diet gourmet specialties)
http://www.raincitygrill.com/
Kingyo (for one of the best izakayas in the city)
http://www.dinehere.ca/restaurant.asp?r=1992
Parkside (on Haro off Denman for one of the best gourmet meals in the city)
http://www.parksiderestaurant.ca/