I'm often out in remote areas with nobody to help, so I've become adept at using a wireless remote and/or timer.
Thinking about it, the only time strangers take my family photos is when they come up and offer. And generally, they know what they're doing. In the same way, if I see someone taking a photo of their family, I'll often volunteer to take the shot so that the whole family can be in the photo. Sometimes I won't even charge for this
There is a good spirit of camaraderie amongst photographers.