Originally posted by Dartmoor Dave use the age-old method of asking a sensible looking passer-by to take a snap of you and your family all together. Most people are perfectly happy to oblige if you ask them with a friendly smile -- and if it's someone carrying a good quality camera of their own then they're likely to get a decent result for you
This is pretty much what I've done. The average DSLR will overwhelm most folks, though, unless as DartmoorDave says - they are toting one of their own. We usually hand them the Canon G15 that my wife carries. The biggest problem is they don't wait for focus, so as DD also notes, it's best to have everything preset as much as possible.
Conversely, if
you are the one toting the big iron, you may get asked to shoot somebody else. I don't mind, and often, either way, a pleasant chit-chat results, too.