Guest attire

You don't.

You can't. Assuming someone can't dress themselves like an adult for a wedding is offensive.

Hope for the best. or hint at how classy the affair will be. I would even talk about some of the attire some of the guest to drop a hint. But if you address them about being "unkept" they will be offended.

You can't decide what a guest will wear or that they should scrub themselves up. Trust in them as they are adults.

The most you can do is write the dress code on the invitation. You can't directly address them.

I would respond like.

You don't. That would be super offensive. What's he supposed to do? Cut his beard for your wedding?

Natalie the only kind of "dress code" is if the wedding is a true black tie event. Anything else, you cannot tell people how to dress.

Let them wear what they want. The worst it will be is you will have one less than perfect picture of you and the couple. The rest will not be that bad and you will barely notice them.

And all other pictures of them can be done in black and white

You could ask your fiancé what he thinks, since it is his family. Maybe he can bring it up. I was the MOH for my best friend, and her in laws felt that "nice" (i.e. no holes or serious stains) jeans were perfectly fine for her semi formal wedding. Her husband ended up telling them that it would really upset his bride if they wore jeans and they showed up in more appropriate attire. It is a sticky situation though.

Telling someone not to wear jeans is a lot different than calling them unkempt.

You can't tell them they have to clean up. You can ask her about what she's thinking of wearing and give suggestions (like you would do with a friend), but you can't control his beard or hair.

You don't- they are adults and you absolutely do not dictate their appearance.

Rude.

Is this for real?

Here's what you do: When they get to the ceremony, whip out a comb/brush and "get those stray hairs in place." Also some wipes and proceed to "just get that little schmootz off" their faces. Lint roller. Shoe shine cloth. Steamer. Febreeze. Done!

His hair offends you?

Richard - would i be annoyed if someone came in jeans - a little. But do i feel the right to do shit about it - nope. They will look out of place

Are they in the wedding or just guests? If IN the wedding..you have more say..otherwise, drink some wine and enjoy your day.

@Richard, I jumped because she doesn't seem to care about her family feeling out of place but more about the formality of her wedding.