The inevitable sequel to little Blue Sky Studio’s 2002 hit “Ice Age” doesn’t fulfill the worst implications of the subtitle and simply dissolve before your eyes. But neither does it take off. It’s a good-natured, inoffensive ramble through familiar computer-animated territory that neither thrills nor appalls. So the question you’ll want to ask is: Is “average” enough for your family outing? Or would you prefer to wait until you and they can view it in the privacy of your own living room?

Whatever you answer, you’ll find that the sequel pretty much follows the pattern of the original, dividing the running-time between the adventures of the acorn-obsessed squirrel Scrat, mute apart from squeals provided by executive producer Chris Wedge, and footage devoted to the trio of Manfred the Mammoth (Ray Romano), Sid the Sloth (John Leguizamo) and Diego the Saber-Toothed Tiger (Denis Leary). In the first installment they banded together to return a lost human infant to its stone-age tribe; in this one they’re already the closest of pals, living with an assortment of other critters in a glacier-bound paradise. Unfortunately, the temperature is rising and the ice melting, and all the varied species begin trekking out of the valley, which will soon be totally flooded, to reach a bark-boat that a helpful vulture has spied on his flights. This “Exodus” section of the movie resembles Disney’s 2000 “Dinosaur”–not a great sign.

As the journey continues, two major things happen. One is that the thaw releases a couple of dinosaur-like fish that come snapping after food. The other is that Manfred, gloomily thinking he’s the last of his kind, encounters a sassy lady Mammoth called Ellie (Queen Latifah). Unfortunately, she was an orphan taken in by a family of possums, and now she not only thinks she’s one but is very protective of her two trouble-making “brothers” Crash (Seann William Scott) and Eddie (Josh Peck), the Frick-and-Frack of the Ice-Age set. Of course, for them to get together Manny will have to convince her about her true species and overcome his own stumbling reticence and prove to her he’s got the courage she craves.

Of the movie’s two parts, the Scrat material is surely preferable. If you were to string all the episodes involving him into a single whole, you’d have a pretty good cartoon, with the squirrel a shorter version of Wile E. Coyote, his obvious model, and the acorn an even less personable version of the Road Runner (if that’s possible). By contrast, the larger story is a pretty pallid business. There’s an effort to pump it up with an assortment of colorful supporting characters, most notably Jay Leno as a fast-talking con-turtle called Fast Tony, and Crash and Eddie are supposed to take up a good deal of the slack. (In truth, they have their moments.) But of the lead trio, only John Leguizamo’s Sid, the obtuse but lovable prankster of the group, really engages the audience. Manny, on the other hand, is a sluggish figure in more ways than one, and his romance with Ellie, voiced without much spark by Latifah, is a non-starter in more ways than one. As for Leary’s Diego, the character’s given almost nothing to do–apart from a forced “you can dn it” subplot in which he must overcome a fear of water to save his friends. The big finale tries to mix action and uplift, but comes across as tiresomely predictable.

“Meltdown” looks fine, with nifty CGI work that improves on the sometimes slightly pale animation of the first movie. There are also some nice throw-away gags, as one involving a dung beetle near the beginning. And we should probably rejoice that the makers chose to go without original songs; the revised lyrics they’ve added to Lionel Bart’s “Food, Glorious Food” (from “Oliver”) indicate what might have been with sufficiently dire force. John Powell’s background score doesn’t get much beyond okay.

And that’s the case with “Ice Age: The Meltdown” as a whole. Like its predecessor, it’s a moderately engaging family movie, but in the Pixar Age that’s not quite enough.