What to Wear?

My husband and I have been invited to a wine and cheese party at the Sheraton Hotel next week. My dilemma is... what do I wear? I'm not too sure if it a casual affair or if evening attire is more appropriate. It is being hosted by one of my son's friends family, and their children will be there. It is mostly going to be attended by dentists and dental professionals. I would think that if there will be children there, it must be a dressy casual affair. I guess that I will have to ask just to make sure. I'd hate to be the family that is over/under dressed!!!