I come from a small town and most of my family will not be prepared to "dress-up" for any event. At most family weddings they will attend in dress slacks, a skirt or what I refer to as a church dress and the men will show up in dockers or even cargo shorts.
I've been married before and it was a very small event in which most of them didn't get to attend (I planned it in a week), so this time I want to all out and make sure everyone is there. However, I want this day to be very special for my fiacncee' and I, so I want people to dress accordingly. Something tells me that if I do not specify my family (and quite possibly some of his) will show up dressed for a bbq

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Any advice on how to let every one know that we want semi-formal or formal attire for all guests? No exceptions!