I don't know what's proper ettiquette, but when I watch Extreme Home Makeover and they have blended families they usually say it like: Swensen Lee family. The example being used from the week before lasts episode where a family (Swensens) take in her sisters four kids (Lees) and they became the Swensen Lee family.
I don't know if that helped you at all or not. Just my own observations.