A. Poskim maintain that one should not enter into a business venture with a Gentile that commercializes with non kosher products (Maharam Shik 136, Rama M’Pano 30, Darchei Teshuva 117: 17 et. al.)
Horav Shlomo Miller's Shlit'a opinion is that one may divide the business into different areas and the Jewish partner should remove himself from the non-kosher food service section of the partnership. Alternatively, an independent caterer could be running the food service section.
A competent rabbi should be contacted to draft the Halachicaly correct agreements between the partners.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a