With your family, brainstorm and create a new family tradition. My husband and I have been doing this, seeing as we're newlyweds. And this would be a great idea if you have an open adoption where you include the birth families in things. Not only would it show the child that they are super loved, but it would make the birth parents feel like they're actually part of the family, and not just some people who allowed you to parent. I know that there have been times when I've felt like an incubator, and that that was the only thing they saw me as. But if you find things to do to include them, they'd feel less that way, and more inclined to get together with ya'll.
If you have a closed adoption then maybe you can figure something out that includes the children's heritage, and your own heritage. Make it all about the children and how special and loved they truly are.