The actress hit up the Happiest Place on Earth Saturday with BF Steve Kazee and Everly, her daughter with Channing Tatum. Everly got the cush stroller ride around the park with potential-future-stepdad Steve on push duty.

Jenna, Steve and Everly seemed to have a great time riding rides and goofing around, and looked totally comfortable with their new family dynamic ... in the wake of Jenna and Channing's split.

That's not to say Channing and Jenna can't get together from time to time for the sake of their daughter -- they did exactly that this past Halloween, posing together for a selfie while taking Everly trick-or-treating.

Successful post-divorce co-parenting has become a thing in Hollywood -- Chris Pratt and Anna Faris most recently got it down pat ... and Chris Martin and Gwyneth Paltrow have been at it for years.

We're all here for this trend.