A source tells ET that the 43-year-old country singer loves spending time with his girlfriend's three sons -- Kingston, 13, Zuma, 10, and Apollo, 6 -- who she shares with her ex-husband, Gavin Rossdale.
"Gwen and Blake do so many fun activities with the boys and Blake plays with them like a big kid," the source says. "He seriously enjoys doing things with the kids like going to the movies, fishing, camping, and teaching them to horseback ride and boating."
"They are both working so much and are loving their life as a family," the source adds of the couple. "Blake has made Gwen's boys a huge priority in his life and cares for them like their his own."
While their relationship, which has been going strong since 2015, is in a great place, the source says that Stefani and Shelton are not eager to jump into a marriage just yet.
"Blake and Gwen are head over heels in love, but don't want to feel rushed to tie the knot when everything is going so well in both of their lives," the source says. "Everyone is asking what they are waiting for, but they really just don’t want to rock the boat."
When ET caught up with Shelton back in June, he revealed how he and Stefani will share the news when they do eventually decide to tie the knot.
"I gotta say that we couldn't be happier, and we've never been doing better," he said at the time. "... I promise you, we won't break the news in any of the grocery store trash magazines."
Another way Stefani and Shelton are thriving right now is through their work as coaches on The Voice ahead of the premiere of the upcoming 17th season. The duo previously worked side by side as coaches on the NBC competition series together during seasons seven, nine and 12. Additionally, Stefani served as a part-time adviser on the show for its eighth and 10th seasons.
"While filming The Voice, they've had the best time," ET's source says. "They’re playful, flirty, and laugh nonstop."
"Gwen seems secure and happy to be back. Gwen has wanted to return to the show for some time, and was in discussions with The Voice, but it didn’t happen immediately. So when she finally signed the deal, she was thrilled," the source continues. "Blake really pushed to have Gwen back after Adam [Levine] revealed he was leaving."
The source also notes that "Blake loves working with Gwen because it really gives them time to be together."
"Blake and Gwen are better than ever," the source shares. "They adore each other. Working together is truly an ideal situation for them."