M.H.
We just did a 50th anniversary party for my grandparents, and used Bennet's BBQ. They come, set up, serve the food, provide iced tea, plates, cups, plastic silverware, etc.... and it seems like it costs between $8 and $10 a person, which is pretty reasonable for a catered meal. Then they clean up, and package up all the left overs. I think they even take the trash. I don't know if that is too much for your budget, or if you need to accommodate a special diet, but they really do a good job.
Good luck with the party planning!
M.