Shaggy Sheep -
I am fully aware of how fun it is to land away from airfields. I rarely land at airfields!
My point is that in this litigious world that we live in, the chances are very high that someone will not see the enjoyable side of it and make the poor chap's life hell. I sincerely hope it goes without a hitch but there is a lot to lose if something gets damaged or there are any BA pilots living nearby (they're the worst for whinging....)
If I was going to do it (and I have!) I would get written permission from the owner (council if it's a state school or trustees if it's a public school) and make sure you have it handy (and I did!)
Make sure someone is on the ground warding off dog walkers, joggers and those people who hang around half dressed in the outdoors at this time of year with their hands up each other's clothes.
Good luck
P.S The choise of a/c concerns me somewhat. Is the PA28 a slab winged 180 or a Charger? If not please be careful....