As things begin to heat up in “The War With Grandpa,” its two combatants agree to rules of engagement.
Similarly, there is a line this family comedy starring Robert De Niro doesn’t want to cross. It works to keep the aging Ed (De Niro) and his sixth-grader grandson, Peter (Oakes Fegley), from becoming unlikeable even as each does increasingly rotten things to the other.
It’s a tall order, considering some of what goes on, but it works enough for “The War With Grandpa” to generate a few smiles and chuckles.
It helps that Ed is a far cry from Richard Kelly, the character De Niro played in the decidedly R-rated 2016 comedy “Dirty Grandpa.” No, this gramps is a sweet if stereotypical older man, one who struggles to use an iPad and who, at worst, leaves a grocery store without paying after becoming fed up with the self-checkout scanner.
And Peter’s a good kid, part of a group of intimidated friends who are entering their first year of middle school. Now the youngest kids at school instead of the most senior, they’re worried about what the older ones have in store for them. (These fears are well-founded, as someone has added “to hell” to a sign that should simply read “Welcome Sixth Graders,” and a bigger kid quickly takes Peter’s backpack off him and chucks it into the trash.)
However, Peter’s bigger problem is at home, because his mom, Sally (Uma Thurman), believes her widower father, Ed, should no longer live alone. While Ed, a retired contractor, doesn’t want to leave the house he built years ago for his wife and him, Peter doesn’t want him moving into his room. (To save Grandpa all the trips up the stairs to the attic, Peter is being relocated there.)
His mom reminds him that his sisters — the older, boy-crazy Mia (Laura Marano) and the younger, Christmas-obsessed Jennifer (Poppy Gagnon) — share a room, but that fact doesn’t bring him any comfort.
Still, when Ed moves in, a dejected Peter warns Grandpa about some uneven floorboards and hugs him but adds on his way out, “Come visit me in the attic anytime — it’s the creepy place with spiders and mice.”
Soon, Peter is convinced by his friends to draw up a declaration of war with Ed and begins small-scale attacks on his elder. (There’s a fun one involving what Ed expected to be shaving cream.)
A little intrigued, Ed convinces Peter to agree to the aforementioned rules of engagements — basically to keep other family members out of it and not to snitch on the other — and Peter agrees to them.
In adapting the 1984 middle-grade novel of the same name by Robert Kimmel Smith, director Tom Hill (“Hop,” “Alvin and the Chipmunks”) and writers Tom J. Astle and Matt Ember (“Get Smart”) avoid turning “The War With Grandpa” into an irritating, slapstick-filled affair. Thankfully, this isn’t a movie full of males getting hit in the crotch. (Oh, it happens. Just not a lot.)
And, sure, Peter maybe kinda sorta puts Ed’s life in danger with at least one maneuver, but, you know, war can be messy. Even as things escalate, that base fondness for each other persists.
What’s disappointing is “The War With Grandpa” doesn’t bring the other family members more into the story. We can’t get enough of the adorable Gagnon, whose Jennifer maybe loves her grandfather as much as she does Christmas.
And the filmmakers have the beginnings of a decent running joke with Ed’s son-in-law, Arthur (a funny Rob Riggle), seeing far more of Ed than he’d ever wish, but they don’t keep it going.
Plus, even though “The War With Grandpa” gets little lifts from the inclusion of veteran actors Christopher Walken, Cheech Marin and Jane Seymour as friends of Ed’s, it fades a bit down the stretch with a rather ho-hum resolution.
Most importantly, Fegley (“Pete’s Dragon,” “Wonderstruck”) is somehow likeable as Peter, even if you can’t condone some of the ways he treats a person many decades older than he is.
And the prolific De Niro (“The Irishman”) manages to give his character that little something extra. You may have expected him to phone this one in, but you can’t say he did.
You also can’t say “The War With Grandpa” is terrific, but it has its moments — and it’s likely to entertain the kids for an hour and a half.
And isn’t that a battle won?
“The War With Grandpa” is rated PG for rude humor, language, and some thematic elements. Runtime: 1 hour, 35 minutes.