Cash-flow mechanism violates tax-exempt status?

My not-for-profit is considering partnering with our local county government to run a public nature center. They'd own the land and building, we'd run the programs and handle routine maintenance. In an effort to ensure oversight, they're insisting on a cash-flow mechanism that would require all income generated on site to be deposited into a special county account. Funds in the account would be dedicated to use at the nature center and we would submit requests to be reimbursed (at their discretion) for our expenses in running and maintaining the facility. We're okay with the concept with regard to admission fees, programs fees, facility rentals, gift shop revenue, etc., but not with regard to monies raised by our on-site fundraising events. We don't think its allowable for us to take private donations and turn them over to a municipality for return at their discretion. Do you agree that the proposed arrangement would somehow be a violation of our not-for-profit or tax-exempt status?