I worked for a movie caterer for 6+ years,
Let's say call time is 7am, your cooks are going to have to start at around 3:30am, prep, travel, set up ready to serve by 6;30 so the crew is ready to start at 7., Lunch at 1pm, lets say 30 min lunch,
tidy up, drive back to the base clean and wash everything, restock, prep, shop etc,...
If there are no hold ups, due to shooting, traffic, etc, they might be done in the 12 hr window.
Can you find a couple of cooks that can work these type of hours, can put out meals on time and understand that if they are 15 minutes late with a meal, it is costing you 1000's of dollars an hour for the crew to sit around and wait for them to serve?
What happens on a day that you go long and need a second meal? Are they going to work 18-20 hrs in a day?
It takes a special breed to do movie catering. We always brought out potential new hires for the day to OBSERVE, paid them $100 cash to go out, most did not make it till lunch. Some would straight out say this is not for me, others would just disappear.
Then you have the cost of renting a truck, insuring it, having health permits, etc.
Food cost, labor cost, don't know how much you plan on paying these cooks, but in 1999 I was making $22.71 an hr, today's rate for a chef/driver is around $38 hr, helper makes around $18, according to a friend of mine that is still in the business.
Remember that a well fed crew is a happy crew.
The other option is having a caterer do a drop off meal service, where the food is cooked at their commissary and brought out in hot boxes.
Are you in LA? or another area?