We have a Harvest Carnival. It is held in the evening and costumes are optional. The kids go from room to room and play games and get candy and little prizes. We sold food last year. It is one of our most attended events. My children love to get dressed up and have a great time.
We don't have one, but if we did - it would need to be "Fall Festival" or "Harvest Festival". Our school traditionally has a zany Halloween theme Track and Field event on October 31st. But definitely, the title is "Fall" Track and Field. I personally don't care if Halloween is in the name, but some people do, and we certainly don't want to offend anyone.
"Fall Festival" don't ask me why when they still let the kids come in costumes. But it's okay with me no problem. We don't have costume contest. Each class can do a scarecrow and have a scarecrow contest or just who ever want to do it. use these to decorate your area? Then there's food and games.