I've volunteered in them before, Chair.
How many kids are you expecting? Ours turned out to be a big party with airplane rides. We had the sign up table, a large grill and a big cooler. The flight school had donated 2 hours on each airplane to the event (we had 12 in the fleet at the time) and the CFIs and line guy pilots all volunteered to fly in addition to the local eaa chapter guys. We had something on the order of 60 kids and at least one family member per kid total for the open hangar. We showed them around our king airs, 3 different models of citations, 3/4 scale P-51 was pulled out by the builder who allowed pictures.
The only thing we couldn't do was get the resturant on the field to pitch in some food as they had a large wedding to host at their party building hence the grill and the sudden increase in Ball-Park stock.
We had:
15 x 172s
1 x 172RG
2 x 150s
1 x Trinidad
1 x Mooney
bunch of ground displays of various kit planes in different stages of completion. We didn't have one experiemental airplane flying rides
I didn't have anything to do with organizing the event. I coordinated with Columbus ATC what we were doing and worked out a route we could fly on a set squawk code without talking to them on every lap and briefing the pilots on what we were/were not approved to do.
Because we had so many airplanes available once we spread the wealth around each kid and a family member got about an hour in the airplane. We set up a big track around the city and for a short few hours our little airport was as busy as any class B airport out there with usually 2 airplanes on final while more were taking off. Good times. Good luck!