Thank you for covering this.
I just wanted to add a few things, to clarify.
Please, please, please dress age appropriately. There is a fine line between "in style" and "trying to be 25 when you're actually 45". There may be some people who can pull it off, but most can't, so be wary.
Also, be at least semi-modest. Everything hanging out is rarely attractive, so cover it up. There is no issue with skin showing, just monitor where that skin is. The other attendees do not want to see your belly-button when you bend over. (This goes for men and women.) Add to the "no-no list" uber formfitting attire. Anything that fits like a second skin is out. Remember, you're there to celebrate the joining of the bride and groom,not how "hot" your body is.
Also be careful to avoid the wedding theme's colors. Ask what the color the bridesmaids are wearing, and avoid it. The wedding party is supposed to stand out.
Assuming there is a reception, and you will be attending, wear something you can "celebrate" in. Whatever form you take part in, you should be able to move in the least. Those who cannot walk in heels should not wear them.
And lastly, your goal in your attire should be to fade into the crowd. When someone first walks in, their eyes should not be drawn to you. So skip the day-glo colors, even though that's what's "in". Eventually, when their eyes do settle on you, they should have the thought "Oh, so and so looks nice."
And that's all. Please heed this, in order to avoid your own embarrassment, and that of those related to you.