Hunting camp: should we lock the porta potty to keep animals out?

Yes, you should lock the portable toilet door to keep bears and other wildlife out. The scent from the holding tank is a strong attractant, and a simple combination lock is the standard solution in bear country. A combination lock solves the problem of lost keys and allows all your hunters to know the code. You do introduce a small inconvenience, but that is far outweighed by the safety risk of a bear investigating the unit or someone having an unexpected encounter. Post a clear sign on the cook tent with the lock combination.

The setup you describe for your hunting camp is correct. A standard unit is appropriate for a dozen people for a week. The gravel pad provides a stable base, and the 30-yard distance from camp is a good balance between privacy and convenience. Your service visit frequency of once for the week should be sufficient, but if your group is large or the weather is very hot, you may want to inquire with your rental company about a mid-week service to ensure it stays clean. The easy truck access is key to avoiding extra fees for a missed service.