I do a lot of fundraisers with frozen product and I sell frozen product at my pizzeria. If you are topping the fundraiser pizzas with meats, you will need Federal Inspections from the USDA. Although those inspections are free, the HACCP, SSOP, and SOP plans can be expensive to get written up. Following the plans is another concern as well. You can check to see if you would be exempt from inspections by packaging the toppings “on the side”.
As far as a freezer goes, we chill to 40 degrees F or less, in our cooler. Then we package the product and freeze it in a walk in freezer. As Tom said, flash freezers are expensive. They are also very small and can only do one pizza at a time (unless you have big $$$$$ and get a large one).
Fundraisers can be highly profitable and bring more customers to your pizzeria. Our business has grown from 750K three years ago (before fundraisers) to almost 2000K this year! If you have a great product that also bakes great at a persons home, you will do well with it. Make sure that you test your product in at least a dozen home ovens. That will help you with your baking instructions for your customers. One other tip: precooking any vegetable toppings are a must. When frozen, the uncooked veggies retain and cook off too much moisture during the finish bake.