It would be very difficult to estimate attendance in this situation, but you could start with some simple assumptions. First, it seems like not long ago that I read that the average American now goes to the movies about 4 times per year. If your area has a population of 100,000, then that would equal about 400,000 admits per year. If there are 35 screens in the area, then 400,000 divided by 35 is 11,429 admits per screen. Of course not all screens will be average. You could assign a weight to each screen. I would think a first run theater would come closer to being average than a theater who shows later run movies. If you look at industry statistics, the vast majority of tickets for any specific movie are sold in the first few weeks up to maybe a month after the release. What is it? Maybe 90%? And, since the competing theaters are multiplexes, they will sit on any successful movie until after sales have completely fallen off.
So, even if your unique concept will draw customers, you have to consider whether or not it will still draw them when 90% have already seen the movies you will show. If the concept is based on food service, then you will be depending more on the restaurant side of the business. I don't have any idea how to estimate number of customers for a restaurant. You need to get even more specific with statistics for a more unique arrangement. However, I would start with the assumption that you will have to work hard to get your numbers up to the average of 11,429. If that will make you a profit, then maybe it would be worth it.
But, honestly, if I were to go out to eat at a movie theater, knowing that this kind of place is not known for low prices, I would certainly want to see something I hadn't seen before. If I were just going to the movies, I might wait to see something at a lower priced place, especially if it were fun or unique. I think that is the appeal of later run theaters... they usually cost less.
Roxy has modest prices and offers a unique experience people enjoy. If you can do the same, then you might be successful.