I forget the occassions, but one time they (I) got her a sterling silver bracelet with two boy silhouette charms. Each had the boys initials as well and their birthdate on the back. I think she has since added different charms w/ their picture inside, etc.
The next gift I got her (perhaps Mother's Day?) was a necklace with two discs w/ the boys' names and attached was their color birthstone. I'm telling you, out of all of the music, gymnastic and preschool classes I attended- I got to hang out with a ton of mothers and this was the trend. It really is the sweetest necklace.
This is similar, except there was one name in the center of each disc and only one stone attached.
So there you have it. Those are great ideas to get for a new mom or mother of young children. :)