Free: Contests & Raffles.
I mean you could just flat out tell him it's only you and him going on the hunt and give him the option of un-inviting the other four. But after he did that to me I don't think I'd trust him anymore and probably wouldn't even want to take him to my spot.
Look....this is your vacation. This is your investment, your family helps you go, you invest all year getting ready for and executing this.