"When we got married five years ago we married the girls, so the five of us always celebrate together," she told PEOPLE at the Women of Worth Awards in New York City on Thursday.
Yearwood is step-mom to Brooks's three teenage daughters – Taylor, August and Allie – and said the whole family has big plans for the anniversary they'll be celebrating back home in Oklahoma.
"We're going to see Tangled," she revealed. "We all talked about it and said, 'Let's go see a movie.' We all actually really want to see it, and none of our children are young young."
The anniversary event is a bit of a prelude to their upcoming country Christmas, which Yearwood said will feature "family, home, just being together – and cooking."
Yearwood presented a Women of Worth award to Taryn Davis, who started the American Widow Project to support military widows, and told PEOPLE she and Brooks strive to teach their girls to give more than they get.
"I hope that my husband and I, through our example and through the things that we do outside of what we do just for us, are teaching our children by example to give back," she said. "There are so many things we can do for others."