Our school actually does what you are looking at, the physical education dept holds a all day agme day. The lower half goes in the morning k-3 and the upper half goes inn the afternoon.
they have a bunch of different stations like balloon toss, sack races, tug of war, etc. The pto is responsible for serving ice cream and drinks.
As far as help it is sort of required that the teachers stay with their class. All special area teachers are also required to be there all day since there is no art, music, computer on that day. Any aides that are in those areas or areas such as library, study hall also have to be there.
We do get alot of volunteers, they send home a flyer looking for parent volunteers and the nice thing is they usually get alot of parents who generally don't volunteer because it is a different type of event. why don't you see about talking to your principal about the staff being there and explain with saftey concerns unless there is supervision you can't do it/ good luck

help!!! my teachers want an all day field day but want to split lower el. and upper el. to each get 1/2 day outside. we asked teachers to recruit volunteers for the day during their time slot, but they came back to say they needed help with that. hellooo we needed help recruiting that's why we asked them! i suggested an after school field day from 6-8 but princ. shot it down. what can we do? our school has 240 students and no one seems to want to volunteer all day. teachers don't want any responsibility during the activities-yet don't have enough parents to make it an all day event.the princ. doesn't want to mix l.l. wiht u.l grades what do i do??? we were also planning on having a fire truck come as well as a proffessional football player. how are all the kids to enjoy this if there split during the day?