Pets and flies; what to do?

Hi, folks. I have a motley crew of rescued cats and 3 dogs. It is full-bore fly season here and I need some method of controlling flies. I would like a non-toxic spray or lotion I could actually put on the dogs and some - any -method of controlling the horrid things in the grass. They just swarm along the ground, in the grass, everywhere. It's easy to find stuff for barn animals but I need to know with certainty that whatever I can find is safe for dogs and cats, especially. Would love to hear anything you've done that's worked.

Alma