I was wondering what is the proper ediquette is for us to do since one of my husbands friends, GRANDFATHER passed away (3) days ago. Do we just send a card? Food for his family? What would be proper?

A card, definitely. Food for the family? That is an honored tradition and you do as you feel led to do. No one can tell you that you have to bring food over. Is there a memorial established, such as donating to a favorite charity? You could do that, in the Grandfather's name. That is optional. It is going to depend on how close your husband is to his friend. One would not expect a casual acquaintance to do what a close friend would do.

Having lost my Dad, I can tell you with complete conviction that anything you do to comfort the family is appreciated and ultimately remembered. As shygrneyzs said, a casual acquaintance wouldn't be expected to make a meal for the family, but if you feel led to, then by all means, make them a meal.

No matter what you decide to do, I would recommend that you mark your calendar for a few weeks out... this is when people tend to forget about the family, not out of spite, but simply because its not as "fresh."

I'd recommend sending a sympathy card and flowers (or donating a memorial in his name) for now, but in a few weeks bring them a meal, cookies, or something that just says that you remember and are thinking of them.

You're being a good friend by simply asking what should be done. I commend you for that. :)