Under no circumstances should notification of a layoff be delayed or withheld.
Layoffs are never pleasant.
There is no gentle way to announce them. The timing their announcement is never right. While the layoff will dampen the holiday, waiting until the day after Christmas to call the affected employees so not to ruin their holiday is absolutely stupid. Consider the impact if they learn about the layoff second hand. It's better to have a tempered holiday with the knowledge of the layoff having been received first hand.