Just as a ballpark estimate, a trip like that in a Robinson R44 would likely be your most cost-effective option, and would take approximately 2 hours flight there and 2 back. Even if you get 500 dollars per flight hour and no holdover charge (which would be a stellar deal), you're looking at a minimum of 2,000 dollars for this trip - probably more.
Now for the bad news and the real answer to your question. Assuming that there are no local airspace restrictions which would prevent you from landing at these schools (and there probably AREN'T... I've landed at schools before for organized educational activities), FAA regulations say that you must have the "land owner's" permission to land at each site. That means it's not enough to get the Principal's sign-off. You'll likely have to get a member of the school board of each district to provide written permission or someone else who is a signatory of the property owned by the school district.
Alternatively, if there are any privately-owned, large, empty fields that are close to the school - say, across the street or something - it might be easier to get one of those individuals to give you permission, and then you could just walk across the street...