When you, a young interfaith couple, come into my study to discuss your upcoming marriage, you might say to me, "Rabbi, we've talked a lot about our different backgrounds and about what we plan to do. We're going to expose the children to both religions. Is there anything we're overlooking or any advice you can give us?"
"How are you thinking about sharing your different backgrounds with these hypothetical kids?" I explore with you.
"Well, we're thinking we'll take the kids to my parents for Passover and to his parents for Christmas."
That's a positive place to start. It will be important to share your kids with your families and your families with your kids. Those intergenerational links will help the kids feel rooted and connected to tradition, however it might be expressed in your two families of origin. Even if one or more of your parents is no longer alive, perhaps you can develop close grandparent-like relationships between your kids and other older relatives.
But there is more to think about than enabling an older generation to share their traditions with your children. You now have the opportunity, as a couple, to choose your own customs and expressions of faith. Your parents may still carry the bulk of responsibility for family religious practice; the older Jewish generation makes the seder, invites the children home for High Holy Days, organizes everyone to participate in family simchas (celebrations), and the non-Jewish partner's parents are also probably taking executive responsibility for the traditions on that side of the family.
As you gradually grow into making your own family unit it will be important for you to start crafting your own choices for religious traditions, beyond being the son or daughter of parents who sustain the tradition. This may be a good time in your lives, pre-children, to explore your options and to engage in deep dialogue about your religious needs and identities. This is a great time to consciously evolve the practices that will define this home.
One couple I know traveled ten hours in a car, year after year, to bring their three small children home to Dad's mother for Passover. One year they told me, "We've decided to make our own seder the first night and go to Gramma the second night. We want to start having some rituals of our own, and we don't want to wait till she's gone and suddenly realize there's a gap."
You can visit synagogues, temples, churches in your area, go shul-hopping, see where you feel comfortable. Maybe there are special programs for interfaith couples. Try on some practices like making a special Friday night meal and lighting candles. See how it feels to partake of each other's rituals or of the set of rituals you have chosen to embrace when you aren't being organized by the parental generation. Together, you might want to think through some of the following questions.
What do you want to be connected to that is bigger than the two of you? Where do you want to make a contribution? Feel a sense of belonging? Be part of something beyond your relationship and family? A community such as a church or synagogue can help answer some of these questions. Or maybe you have a secular group that is meaningful to you, such as the folkdance community, Greenpeace, or a twelve-step program.
People sometimes think of organized religious life in a negative way--it's an "institution"--but really one of the purposes of a religious institution is to be a caring community, to embody God's work in the helping hands that support each other in times of need and celebrate at times of joy. Without being part of the mutual give and take of a real community, a couple can become isolated. Being part of something bigger than yourselves gives meaning to life.
So, yes, I do have some rabbinic wisdom to offer in response to your query. Don't think of your quest as something you are doing on behalf of your children. Make it your own; find places and practices, holy ways and holy days, that work now for you as an adult member of a couple. This is the best gift you can give your unborn children.