The reasoon this old wives tale exists is the same reason the tale about people going mad on the night of the full moon exists. When there's a beautiful full moon out, like there is right now, people are more likely to be awake and active at night. This is especially true in less developed societies with little or no electric lighting. Combine this with the fact that, in general, mammals prefer to birth at night when it's easier to hide a female's complete vulnerability during labor and their bodies are designed to accomodate this. Now, you're up late...walking around or having intimate relations (which if nothing else will widen the passageway)...at a time when you're already primed for birth....viola!
So, my suggestion?
Have a glass of wine tonight with your husband (it's not going to hurt anything at this stage, but it will relax your muscles). Go for a walk in the moonlight. Try to have some intimate relations. And then pray for labor to begin, because these actions are still just about as likely to induce as anything else.
Best of luck.