I'm thinking that your mainly speaking of the "friends" of the members. Of course you won't be able to keep the members out, unless at the end of the year you don't renew their memberships.
I'm not real familiar with hunting camps. They're not real common in my state. I do have several buddies down south that pay a fee (around a thousand per year) and can hunt 2,000-3,000 acres. They've offered me to come down and hut hogs with them if I pay the "friend" fee that is around $25 per day. Perhaps if that's what you're referring to, your camp can eliminate the "friend clause" and just say members only.
I'm assuming that because your grandfather owns the land, he can make his own rules up. The only down side that I can see is that if you upset too many members and they don't renew their own membership, then you could lose revenue, assuming your using their membership fees to pay for the land or the taxes.