Hey Russ,
Better check the local laws and such before you begin, if you are doing this to "wan't to make at least something for my time". That by definition is a for profit venture.
Typically you must meet the local licensing board requirements and be licensed if you are even thinking about charging these folks. Otherwise you can get fined. If you are doing it for charity, then there are usually allowances made (like for churches, Boy Scouts, etc.) to have fund raising events.
Also do you have the insurance necessary in case someone gets sick and sues? A friend you may think is a friend, but after 3-4 days in a hospital with food poisoning or even an unrelated illness that that person thinks that they got from your cooking and next thing a process server knocks on your door. Check with your local health department...typically you must have a dedicated kitchen (NOT in your home) to do this.
If you are just doing a cookout for such a large group of friends who will chip in for the costs approach with caution, ensure that your salads (cold foods) are kept at 40 F or below and that your cooked foods are maintained at 140F and above. Take temperature readings and document in a log book...so if there is a problem you can demonstrate that you made the attempt to properly serve food.
It takes an investment of time and money to get into the catering business...you need to make sure you do it right.
Check the link below to the University of Georgia Agriculture Extension service bulletin on BBQ Catering:
Catering for Small/Large Groups
Don't mean to sound negative or over cautionary and I wish you best of luck...
Preston D