The biggest problem you'll have tethering 2 dogs is that they will get tangled up with each other unless you tether them on opposites of the campsite to the point they can't reach each other.
You can use a double leash to reduce that. Attach the double leash to the dogs, then use it to attach them to the tie out. As another poster mentioned, run the main tie out across the site up in the air, then use a shorter tie out to attach to that and the dogs' double leash. This will help keep them from tangling up in each other and in other things.