I spent last summer studying and relocating Western Rattlesnakes (Crotalus viridis) in British Columbia. Studies have shown that in Long-distance Translocations (2km and more) mortality rates are extremely high. I routinely translocated up to 1km (0.6mi) with no observable adverse effects on the individuals. These translocations certainly do not seem to deter them from returning though, and I would sometimes have them back within 2 days. Usually though, it does buy a little more time than that. I'm not sure exactly how this info will pertain to Copperheads, but I would caution against moving them too far.

It's great to hear about someone relocating, as well as creating suitable habitat, so many snakes are killed by intolerant homeowners. I do understand though, the concern about family and pets. Best of luck with whatever course of action you take, hope this has been a little help.

Cheers,
Kyle