I would get the HD inspector to your location and have him give you a ruling. It won't matter what we hear or say, the inspector will have the final say. I would think that if your trailer kitchen is certified as a commercial kitchen you could do your prep in that. But like I said I am not the inspector and will not be making the decision.
Team: Pyle's BBQ; Yoder YS640; Good-One "Trail Boss" 60T; Weber Kettle w/rotisserie ring; Big A$$ Rotisserie; Weber OTS; New Braunfels offset smoker.
Saddles BBQ Bistro