Rodney

"Mr. and Mrs." at first, just to be formal, then first names. After all, they're calling you by your first name, and you're not their kids. If you want to be totally cool about it, tell them you'd like to start calling them by their first names. They'll be fine about it. Usually. There are exceptions....

I knew a woman whose mother-in-law decided that she wanted her daughter-in-law to call her "memsahib" -- which is more or less Indian/Pakistani speak for "big momma head of the household." Now this woman wasn't from India, but she'd lived there as a wealthy woman and that's what her servants had called her. My friend refused to call her memsahib, especially since she didn't ask it of her son-in-laws or daughters. But this woman "just couldn't figure out" why her daughter-in-law didn't want to call her by a name which connoted submission and wasn't required of anyone else. So in the end, her daughter-in-law doesn't call her anything!