I see this as a golden opportunity for you. Why not go to your client with suggestions on how to make these shows look better? Approach it in a positive light. Tell the client that if they were to shoot cutaways and vary their angles or focal lengths, you, as an editor would have more to work with and be able to provide him a better looking show.
Of course be careful that the client’s shooters aren’t family members, good buddies, or the client himself. In that case bite your tongue.
Explain to him that you’re running into challenges with audio, and you’d be happy to even talk to the folks shooting the video for him to help him achieve a better quality end product. What I do is explain how it takes longer to edit poorly planned or shot video, and poor audio. If you’re charging him an hourly rate explain to him that you can edit faster and ultimately cheaper with better quality. If he disagrees with you… you can always move on.
Good luck