"Our first day of the Storyteller Tour, my son Isaiah walked for the first time," she says in a new interview, taking ET exclusively behind the scenes of her new show. "Now he's four and we're on the Cry Pretty Tour. I just know we're gonna have many more milestones with him and with Jacob, who is three months old."
Underwood's two young sons will join her on the road, along with opening acts Runaway June and Maddie and Tae.
"It just makes my heart happy [that] I have the kind of job where I can bring my children with me and they can be a part of it," Underwood says. "My work and my life kind of collide all together and it makes for a big, wonderful mess."
The 55-city tour kicks off Wednesday in North Carolina, and when it comes to Underwood's grueling schedule as a working mom, there's at least one aspect of life that gets easier on tour.
"I don't have a house to clean," she laughs. "I don't have as much laundry to do. I get to work out more consistently when I'm out on the road. I can't get up there and do what I do how I would like to do it if I'm out of shape."
Underwood recently opened up about her body image insecurities after welcoming her second child. In a post on Instagram, the 36-year-old singer admitted that "bouncing back" has been tougher the this time around. In a lengthy, heartfelt caption, she promised herself to "start appreciating what my body CAN do and stop focusing on what it can't."
In addition to putting on an epic show for her fans, Underwood is also focused on continuing her mission of giving back to underprivileged kids.
"A few tours ago, we started doing a thing where we would donate a dollar from every ticket to a charity," she explains, noting that money from the Cry Pretty ticket sales will benefit Danita's Children in Haiti. She and husband Mike Fisher have long been supporters of the organization.
"It's just a special place. We've been there, we see the kids, we know exactly where the money that we've donated over the years goes," she says. "That's so important to us. We're saving lives just by being at a concert, and I think that's the coolest thing ever."
Underwood says that every song on her Cry Pretty album will be represented on the tour, and that fans can expect to see a version of her CMT Artists of the Year medley alongside her opening acts.
"Oh lord, I am not going to cry this time," Maddie and Tae's Taylor Dye jokes. "This tour has completely changed our lives, 100 percent. When we got the call that we are going to get to tour with one of our favorite artists in this whole entire world of music, not just country, it just, I mean, it felt completely surreal."
Adds Maddie Marlow, "Hopefully we walk away from this tour as much better artists, but also better people. She's a great performer, a great wife, a great friend, a great mom, so I think we are going to be gaining all the wisdom nuggets and just walking away with so much to give to our next show somewhere."
And the opportunity to perform as part of an all-female lineup isn't lost on Runaway June.
"I think this tour is important because there's been this really loud conversation going on for a couple years now about the lack of women on concert venue bills and on country radio," says Naomi Cooke. "It's really, really nice to be a part of something that's actually moving that conversation forward now. ... And [Carrie is] doing it in the best way, too. She's saying, 'I didn't pick these acts because they're women, I picked them because they are the best acts for the show and it's going to be a kickass show.' And I think that's really, really important and that's really strong."