Hollywood has a heck of a time delivering family-friendly action films that don’t make adults groan for 90-odd minutes.

“Journey 2: Mysterious Island,” available on Blu-ray Combo pack, DVD and for download tomorrow, struck a box office chord precisely because it walked that delicate line, the one proudly labeled “PG.”

Dwayne (don’t call me Rock anymore, please) Johnson stars in this sorta-kinda sequel to Brendon Fraser’s “Journey to the Center of the Earth,” although the new film is superior in all the ways that matter.

Johnson stars as Hank, the world’s must muscular stepfather, who takes a trip with his reluctant stepson (returnee Josh Hutcherson) to an uncharted blip on a map. They’re joined by a goofy pilot (Luis Guzman) and his beautiful daughter (Vanessa Hudgens).

They all end up at the center of a swirling tunnel of air, the kind Jules Verne promised would lead to … a mysterious island. One hyperactive special effects sequence later, and the quartet is stranded on the island, a gorgeous place where the elephants can fit in your hand but the bees could bowl over a Pontiac.

The group soon discover why they were summoned to this spot (Michael Caine, grinning at how easy it is for a cagey pro to pick up a paycheck, plays the lad’s grandpa). Together, they try to flee the island before the water rises around them.

The film’s 3D origins lead to some distracting sequences – who on earth thought it was funny to build an entire scene around Johnson’s bouncing pectoral muscles? But the banter here is light and occasionally witty, and Johnson’s manufactured grins are feeling a little less forced these days.

Baby steps, right?

The visuals, including some beautifully drawn landscapes, betray their digital origins but still look smashing in HD. The action sequences will scare some tykes, but there’s nothing gratuitous or punishing about them.

Johnson and Guzman share a goofy chemistry that mostly works to the story’s advantage, and the screenplay doesn’t overplay the natural stepfather-esque tension between Johnson and Hutcherson that could easily be parlayed into empty dramatic calories.

The Blu-ray extras include a gag reel, deleted scenes and an interactive map meant to show the young ones all the danger lurking on this “Island.”