Kylie and their kid were arms up as Travis performed to a sold-out crowd at The O2 Arena ... which held 20,000 screaming fans.

This was Travis' first arena concert since the Astroworld tragedy last year, and it went off without a hitch ... well, actually, one idiot threw some sort of heavy object on the stage, missing Travis, but he was clearly pissed.

He has another show Sunday night, and he seems thrilled to be fully back.

The rapper wasn't holding back much, if at all. He was all over the stage with max energy, but he was clearly mindful of the crowd ... not wanting to encourage them to go too far.

Travis acknowledged K&S were in the crowd, and then dedicated "Mamacitas" to his daughter. Their baby boy, who was born in February, wasn't at the concert.

Travis intro'd a new song, "God's Country" ... it was supposed to be on Kanye's "Donda" album that was released last year, but didn't make the cut.

There were other celebs on hand ... Kevin Durant and James Harden were backstage popping champagne bottles and dousing their buddy Trav.

After the concert, Travis and Kylie were interlocking fingers as they made their way to a restaurant ... the hard-to-get-in The Twenty Two. Somehow they got a res!

Kylie and Storm had some serious mommy-and-me time all week in the town of Big Ben, shopping and just hanging out.