THE WAR WITH GRANDPA: Welcome back to the movies

* * 1/2 (out of four)

After a few previews that preceded “The War with Grandpa,” Williamsport’s AMC theater ran a full-screen shot saying “Welcome back to the movies.”

That pretty much cemented the pleasure I felt upon settling into my seat at the downtown venue; and this feeling may also be one reason the modest crowd and I laughed our heads off at this uneven and occasionally very silly feature.

It’s not great, but it sure was fun; and that’s something most of us could use right about now.

Robert De Niro plays a grumpy grandparent who moves in with his daughter’s family, taking the room of his 12-year-old grandson, who is in turn relegated to the attic. Egged on by his sixth-grade chums, young Peter declares war on the old man, rigging various childish but effective booby-traps in an attempt to reclaim his household territory. But Grandpa, a handy one-time home-builder, still has a few tricks up his sleeve.

All this results in a series of slapstick pranks that are sometimes quite amusing (i.e., a swap-out of shaving cream, two mishaps with a motorcycle cop and a comical dodgeball match -- in which the young square off against the old).

De Niro never hams it up unduly, and the same goes for Oakes Fegley (“Pete’s Dragon,” “Wonderstruck,” “The Goldfinch”) as the adolescent assailant. Among other things, De Niro brings a fitting gravity to the film’s few serious scenes, in which the elder fighter tells his grandson that, based on his own experience as a combat veteran, war always sucks, even for the winner. Acting-wise, Poppy Gagnon also fares well as Peter’s likable little sister.

I’m afraid the same cannot be said for the rest of the film’s impressive cast, which includes Rob Riggle, Uma Thurman, Christopher Walken, Cheech Marin and Jane Seymour. The beloved Thurman, once one of the hottest actors on the planet, really feels like she’s slumming it here -- as do both Walken and Seymour. That, however, is mostly the fault of the script; it gives them basically nothing worthwhile, and that is exactly what they do.

This lapse is particularly painful in the case of singer and actress Laura Marano as Peter’s older sister; her surly teen character is so thin and stereotyped that she’d be better off written right out of the film.

Nonetheless, the movie works nicely for about an hour, before going way over the top in its final party scene, which isn’t nearly as funny as it thinks.

Critics have really savaged “Grandpa,” giving it a dismal 26% rating at Rotten Tomatoes. That site’s audience approval, by contrast, stands at 88%.

You can put me firmly in that latter group; and if laughter is any indication, I dare say the other returning patrons in the theater liked it even better than I.

“The War with Grandpa,”

directed by Tim Hill

Run time: 94 min.

Rated PG for mild rude humor and thematic elements