I have this situation...and
Did you forget to lock the door or what?
You said," I feel that giving the key to a family member is better than a neighbor. "
At least your MIL might start wearing less perfume, since she now knows that its giving her away!
Do you have a neighbor that is usually home and that you would trust with a key?
I heard a home security lecture in which the police officer said that the thieves see the same ads as the rest of us for the fake rocks and hollow soda cans etc. sold for hiding keys or valuables. To the wrong person that fake rock says "just let yourself in"!