I have been the business advisor on many restaurants. The first, Victoria Station, was in the late 1960s. It grew to become a chain of 100 restaurants. Another was Green's at Fort Mason. Greens is a high quality vegetarian restaurant with over 180 seats that has been full throughout its 33 years of existence. That is a hell of a long time in the restaurant business.
Whether a restaurant will be a success or not has to do with hundreds of factors.
Whether it CAN BE a success is a different story. It is so rare, as to be almost nonexistent, for a restaurant to open slowly and grow slowly to reach capacity and success.
From my experience, if a restaurant is to be successful, ever, it must open its doors at full capacity.
It doesn't really matter how the customers come to the initial opening, whether it is because they are friends, because they have personal invitations or whether they get special treatment.... none of that matters. What matters is that the restaurant opens full of people and remains full of people for the first weeks and months.
You will often see a full restaurant next door to an empty restaurant. It is my experience that the full restaurant opened to capacity and the empty restaurant opened nearly empty.