It is most definitely proper for you to send announcements to people whom you'd like to have at the wedding but can't squeeze in. It's even proper to send announcements to people whom you wouldn't ordinarily invite, but who might be pleased and interested to know about your son's marriage.
The purpose of an announcement is simply to announce that a wedding took place. Receiving one creates no obligation to send a gift or card. Some of your more enthusiastic and more organized relatives probably will send some token of good wishes, but this should not be expected.
Since the wedding announcement informs people of an event that has already taken place, it is sent so that it will be received after the wedding. The usual practice is to order the announcements at the same time as the invitations, address them in advance, and then drop them in the mail on the morning of the wedding. This practice isn't mandatory, just convenient!
If the bride's family is financing the wedding and they are not interested in sending announcements, you can still send announcements to your friends, at your own expense. You don't need to worry about whether the announcements match the invitations, as no one will receive both.
The traditional wording for announcements is very simple. If the bride's parents do the announcing (in which case, they've asked you for a list of people to receive announcements), the wording is:
Since announcements typically go to friends and family who are not in frequent contact with the happy couple, it is very helpful to include information on where the couple will live after marriage and what names they will use. Most invitation companies can provide an "at home" card, which is a small card designed just for this information. If this card isn't available or doesn't provide enough space, you can also have the information printed on a smaller-sized reception card- or on normal business cards, at any printing shop.
What information belongs on an "at home" card? First and foremost, the couple's post-marriage names, with titles! Check this one carefully with your future daughter-in-law. If she prefers to be called "Dr. Jane Jones" after marriage, and you've sent 50 relatives cards that refer to her as "Mrs. Peter Jones," she will not thank you for the help. The card should also include the couple's post-marriage address, phone number, and, if the couple cares to include it, e-mail address(es). An "at home" card looks something like this:
While looking for wedding announcement examples from real couples on the Web, I discovered that many couples use "announcement" as a synonym for "invitation." The two are not the same thing. A wedding announcement must never be sent before the wedding. To prevent misunderstanding, the best thing you can do with an announcement is to keep it as strictly factual as possible.
If you order announcements on your own (not as part of the bride's invitation order), you can order from almost any local stationery or card store, or you can start with mail-order catalogs. Catalogs for several of the major mail-order suppliers can be ordered with one visit to Wedding Paper Divas. Be a discerning consumer with these, as paper quality and service can vary widely. And enjoy!