The amount charged for the event would depend on what is to be served. There are two ways to approach the matter: you can determine the budget (cost per person x number of people) and then decide what kind of menu can be provided for that price; OR you can create two or three different menus and cost out each one, then determine the per head price based on the total amount. It is not possible to give or get a quote for "30-50 people." It is possible to get a per person dollar amount and agree to the date upon which the final count will be phoned in. The amount of insurance depends on the location, the date and time, the group, whether alcohol is involved, whether open fires will be used for cooking, etc. The cost of coverage can be provided by an insurance agent; start by calling the one that handles your homeowners or auto coverage.