While so many things will be different for Céline Dion this holiday season, some family traditions, such as singing carols on Christmas Eve, will take on greater meaning as the family prepares for what might be their last holiday together.

“They spend hours singing traditional carols—and no, Céline doesn’t just belt them out solo!” reveals an insider. “It’s a real family sing-along.”

celine dion and rene angelil

Céline and René in 2013.

The throat cancer that has ravaged the health of Céline’s beloved husband, René Angélil, 73, won’t allow him to join in the singing.

But the sight of Céline, 47, and their sons, René-Charles, 14, and twins Nelson and Eddy, 5, laughing together will certainly fill René’s heart with joy.

RELATED: Céline Dion Performs Emotional Paris Tribute at the American Music Awards

Unless there is a miracle, “this is very likely the last Christmas they’ll celebrate with René,” confides the insider. “But Céline is hopeful by nature, and she puts her trust in her faith. She’s trying to make the most of whatever time they have left with René.”

celine dion, eddy and nelson

Céline with twin sons Eddy and Nelson in October 2015.

And as the holiday season begins, Céline, who is on a break from her Las Vegas show at Caesars Palace until Dec. 30, is determined to keep the mood at home light and merry.

RELATED: VIDEO—Céline Dion Gives Touching Tribute to Cancer-Stricken Husband René Angélil During Concert

“She won’t allow the house to descend into gloom and doom. She does her best to fill her boys’ lives with fun and excitement,” says a family friend. “But I also think that every day has become more meaningful to them given what the family is going through.”

To read the full story on Céline, pick up the new issue of Closer Weekly, on newsstands now!