So are you going to be using airplanes they own? Cause you'd be "operating under their certificate" regardless. If you are going to buy your own airplane, and charge people for flying on your airplane, you need a charter certificate. Even if you aren't going to charge people directly for the flight, but you are going to use this airplane as an incentive for going to your ski resort, or whatever, you need a certificate.
What you need to do is sit down with management from a local charter company, and go over this stuff face to face. You'll get a much better idea of what they can and cannot do, and get an idea on how much this will cost. It will be a much better use of your time vs a bunch of idiots like me trying to give you advice on the internet.