I've been invited to give feedback to all Parsons students, regarding your thesis projects.
Solari is a great idea at a time when whole food nutrition for both our bodies and our environment is critically important. I like that you suggest implementing this into elementary schools, for starters. (Get 'em while they're young!) Look into the case studies from Curitiba, Brazil, where Jaime Lerner implemented a recycling program that started with the young children, who then went on to teach their parents. Like your project, this is far more effective than doing it the other way around. Bottom-up environmental education has the potential to bring about greater, lasting impact than top-down enviro-education.
You've also hit the nail on the head with the accessibility issue. We tend as a culture to eat "junk food" because it's all around and far more available than healthy, whole food. Once this gets turned around - when the good stuff becomes just as available as junk - then we'll be more empowered to choose the real food solutions. Finally, partnering with local farms is great. As is getting the students involved in working the cart at school. Perhaps the students could alternate shifts and be accountable for certain crops?
Good luck testing your prototype. Yum! J.