Im having a big summer party with 100 r more guests how would i reheat burgers after cooking then on a bbq?

I've done some catering and sometimes you cant help but prep the food bc you don't have the equipment in your back yard on a daily basis for 100 people. So I agree to cook them med to med/rare and place in a large aluminium tin , covered, you could do the same for the hot dogs or other meats, and then simply buy a little bunson burner for underneath . This will keep them warm without drying them out. good luck!