My dd's school encourage it to be a family even, there are about 70 students and they included a teacher parent relay and a race for preschoolers. Kids were encouraged to eat with families at lunch or sit with their friends. The volunteers did some work but the school arranged for the Local Lions club to cook the BBQ (school supplied the food)

I think making these things family events is great and create a sense of community done well but if poorly organised I can understand how it could quickly turn to chaos