Sometimes it's a matter of using the flash sparingly with only a dome diffuser by a light wall and usually for skin tone consistency. I then balance it to the ambient in the background adding a sense of place with a more natural, environmental look. If there's room, then I can use a soft box or umbrella. Each case is different and sometimes I'm lucky and the light is perfect without the need, but that's rare. I'm more likely to to shoot the family in their yard, especially if the family is more than just a few members and then I'll light it with a large octadome which can light a fairly large group and add separation from the landscape.
My goal with these situations is to minimize the intrusion, minimize the lighting and maximize the uniqueness of the image all to tell a story, rather than simply recording a bunch of faces.