Question about frittata mixture?

I have to make a frittata in 2 days for a large group of people, approximately 72. I work in a school and once a month we bring in breakfast, and this month it's my groups turn. School starts at 8 am and we have to have the breakfast there no later than that time. So I'm making for pans of frittata and planned to make the vegetable mixture the night before so that in the morning I just need to put the eggs in the pan with them and bake it. So my question is, can I beat the eggs the night before and put them in a sealed bowl in the fridge overnight? And also, can I cooke the veggie mix the night before and will it be okay in the morning and not soggy? I'm going to use onions, cubed potatoes, spinach, mushrooms and some peppers. If I cook them in the morning, it will just take too long, so this is why I want to precook them the night before.