Holidays with children are family activity, not couple time. Parents who never take a holiday alone together gradually lose the relationship that produced the family. One parent-only holiday yearly (even a long weekend) maintains it.
What this requires
Grandparents or trusted childcare. Defined dates (calendared months ahead). Trust in childcare and lack of constant checking-in. Two-three nights minimum.
Why it pays back
Marriages with deliberate couple time stay stronger through parenting years. Children benefit from parents who are still in love. Most couples who try this annually wonder why they didn't start sooner.