Wedding guests need to be welcomed by the marrying couple, who offers them little presents, that will remind the guests that they have participated at that particular wedding. And a couple that wants to stand out from the crowd can use differentiated gifts for their wedding guests.
For example, for their parents, they can buy something more expensive, such as watches for their dads and a beautiful jewelry set, containing a pair of earrings, a necklace and a bracelet, for their moms. For their siblings, they can buy photo albums, jewelry as well (if they know their sisters and brothers to wear such jewelry pieces), decorative objects, clothes (here we are talking about sisters and brothers, not about aunts, uncles, nephews and nieces, so we assume that the bride and groom know the measurements of their sisters/brothers), gadgets, mugs, hats, or any other products.
Well, for those families that will be present at your wedding, families that have collected a number of years together, you and your partner could consider buying some anniversary cards. This is available if you know that family very well and if you suspect that they will like those anniversary cards that you will offer them.
An anniversary card is usually bought by a couple that celebrates 10, 20, 30 and so years of existence, not by another couple who wants to offer those anniversary cards as a gift for being present at a wedding, so buying anniversary cards for a couple like this should be done only if you are certain that they will love your present and they will actually use it.
After the couple that receives those anniversary cards gets home with them, it is supposed that they will start spreading those anniversary cards to their friends and family, inviting them to their anniversary.
Many marrying couples are afraid to offer such gift, because they believe that by offering some anniversary cards to another couple that celebrates 20 years of existing let's say, that couple will be obligated to invite the marrying couple to their anniversary as well. But this should not be an impediment in buying a gift like this. Let's face it, you will never buy such gift for a couple that you barely know. And if you don't know that couple, most likely you don't know when they got married and when they will celebrate their marriage, if they plan to celebrate it. So you definitely need to know the couple for which you will buy those anniversary cards.
If you don't know whether buying anniversary cards for some of your wedding guests is a good idea, you should discuss this matter with your parents; ask them if they would be happy to receive such presents from a recently married couple, at that couple’s wedding. See what are their opinions and try to make a decision based on that.