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As the parents of four children in the 1950s and '60s, Susan and Mike Levy had a Christmas tree in their house — even though they raised their kids Jewish — until their oldest child was 14.

Not surprisingly, some would say, three of the four kids grew up and married non-Jews.

Now as grandparents who care deeply about their Jewish heritage, the Levys are in great pain. All six of their grandchildren are being raised as Christians in completely non-Jewish households.

Susan Levy will talk about how she deals with those emotional and often volatile issues at "Building Jewish Bridges." The workshop for interfaith couples, their extended families, rabbis and other professionals takes place Sunday, Feb. 13 in Berkeley.

"Grandparenting the Child of an Interfaith Family," a workshop with Levy and two other grandmothers on the panel, is only a small part of what may be the most comprehensive conference of its kind over held in the Bay Area. More than 100 people are expected to attend the event at Lehrhaus Judaica.

"It's the first conference in the nation that includes both the professional people and the lay people," said organizer Dawn Kepler, Lehrhaus' community outreach director.

Rosanne Levitt, an interfaith counselor who will be the moderator at the grandparents' workshop, said the Bay Area has never been host to a bigger conference on interfaith issues.

"I'm very excited," said Levitt, the director of the Interfaith Connection, a project at the Jewish Community Center of San Francisco. "Usually these conferences take place on the East Coast, so I'm thrilled that we're having this opportunity in the Bay Area."

Interfaith issues are seldom easy to deal with, and the grandparenting workshop will address several thorny issues, among them: dealing with guilt, addressing feelings of betrayal, minding one's own business, not ruining one's relationship with one's children.

Levy, a 38-year resident of Oakland, said knowing that her grandchildren have practically zero Jewish upbringing and that five of the six go to church regularly often tears her up inside.

She is sometimes angry at herself for perhaps not giving her children enough of a solid Jewish foundation, and she is sometimes mad at three of her four children for completely turning their backs on Judaism.

Through it all, however, she feels the best strategy is to bite her tongue.

"We're accepting of it for the simple reason that you want to have a relationship with your children and grandchildren," said Levy, a longtime member of Oakland's Temple Sinai and the chairperson of the Reform congregation's membership committee.

"We're accepting of what our children are, and we have a good relationship with our grandchildren. That's important. I would hate to be hard-nosed and not be able to have a warm relationship with them."

Levy said her household was "not terribly observant," but her children did go to religious school. Their oldest daughter was confirmed; the oldest son celebrated a bar mitzvah; the two youngest daughters had both confirmations and bat mitzvah celebrations.

Yet only the youngest daughter has married a Jew. One of the children got divorced, only to once again marry another non-Jew.

Often, seeing their Jewish children marry outside of the faith — especially for parents who were secular and tried to assimilate — isn't intensely painful until grandchildren enter the picture and one's heritage comes bubbling out.

"I know one grandma who says, 'I'm the Jewish grandma and the other grandma is the Christian grandma,'" Kepler said. "They feel responsible to carry that torch, even though maybe they never even celebrated Shabbat."

Levitt has seen that scenario, as well.

"If the children choose another religion, then the question grandparents face is 'I want my Jewish tradition to live on, so how do I share that with my grandchildren?'" she said.

"What I advise is to ask your children's permission to do that. If you find it important that the grandkids know where they came from, the important thing is not to do it behind their back, not to be sneaky, but to be very open about it."

Levy, for example, said her grandchildren get to experience Shabbat when they're visiting her house in Oakland. "We try to explain what we're doing and why we're doing it," she said. "I think they know how we feel and are respectful of it."

That works both ways. When Levy visits her daughter's house and sees "all of the Christmas trappings, it gets to be a little much." And when her daughter wears a cross "in my house, that's kind of tough. But my husband and I have talked about it, and I'm not going to say anything."

Joel Crohn, a therapist who specializes in interfaith issues, said Jewish grandparents often don't know who to turn to in dealing with their intense feelings of anger, betrayal and regret.

"Some grandparents go to rabbis, who in turn come to me in my office and beg me to help them deal with it," said Crohn, who has offices in San Rafael and Kensington.

The therapist said the difficult issues for grandparents are no different from those that may cause problems in many interfaith relationships.

"This whole conference is about building Jewish bridges. It's to provide workshops for rabbis to help them deal with their mixed feelings. It's for rabbis and therapists to come together and talk about issues," he said.

"For grandparents and everyone else, there isn't one answer that fits all cases. This conference is all about providing people an opportunity to dialogue."

The conference will offer 10 workshops designed for people trying to deal with interfaith situations. There will also be five workshops for rabbis, other clergy, teachers and community professionals.

There will be three keynote addresses, each approximately an hour, which will be attended both by lay people and professionals.

Prominent figures in the field are the keynote speakers: Egon Mayer, a Brooklyn College professor of sociology and the director of the Jewish Outreach Institute in New York; Crohn, who has written "Mixed Matches" and is the co-author of the forthcoming "Fighting for Your Jewish Marriage"; and Bruce Phillips, a demographer and professor of Jewish communal studies at Hebrew Union College-Jewish Institute of Religion, Los Angeles.

The conference is the culmination of two years of classes and workshops about interfaith issues funded by a $66,000 grant from the Walter and Elise Haas Fund.