I didn't assume anything. You didn't know Ohio hunting laws or you wouldn't have asked the question. All the rules can be found at
http://wildlife.ohiodnr.gov/huntingandtrappingregulations.
This winter I gave someone permission to hunt waterfoul on my property. My rule is, and I told him about it in my initial conversation with him, is that I have a copy of the hunter's driver license and that I mail the permit to them. The permit states what may be hunted and releases me from all liability for them being there which, as a landowner, I think is reasonable. The guy wanted to hunt the next day so I made an exception and told him he could. Within an hour after he left he called me asking me if a buddy could hunt with him. He knew my rules and had to ask that question? No. I kindly made an exception for him but that doesn't mean carte blanche for his buddy. It did have a happy ending for him; he had a great hunt, killed a bunch of ducks and geese and thanked me profusely. That said, don't make it inconvinient for the landowner. I prepare the permit, I pay the postage and my charge for the privilege of hunting on my property is ZERO.
Several years ago I was in a similar situation as are you. Someone who had permission to hunt deer on another person's property invited me to go with them. I said no; not unless I'm given written permission. I play by the rules.
In Ohio, to hunt on another person's property requires written permission whether or not the land is posted. In Pennsylvania, where I used to live, the land has to be posted every few feet so, what do the hunters do? They tear down the signs and hunt anyway. I had to discharge quite a few of them. The solution is to call the police and make a record of the trespassing and then for subsequent violations one has a case for criminal tresspassing. My patience with tresspassing nonsense has worn very thin. Both I and my wife want to know who are on our property and when they're there.