The schmaltz is piled on thick, and if the comedy were any broader it would require an Imax screen, but still there's something touching about how hard Billy Crystal and Bette Midler hustle to peddle the threadbare material that makes "Parental Guidance" a perfectly tolerable, if uninspired, moviegoing experience.

As "the other grandparents" who are given a golden opportunity to bond with their seldom-seen grandchildren, Billy and Bette work double-time, well aware that it's not just the juvenile characters they have to entertain, but also the paying audiences who could count on both of them for a good laugh back in the day.

That they manage to pull their weight even when the achingly formulaic plotting threatens to drag them under is a testament to their "let's-put-on-a-show" spirit. The end result should appeal to audiences, including bonding grandparents and grandkids, looking for a little undemanding holiday cheer.

Crystal is Artie Decker, who has just lost his longtime gig as "De Voice of the Fresno Grizzlies" when the minor-league baseball team decided to upgrade the outfit with the sort of talent that knows its way around a Facebook page or a Twitter account.

Already despondent, he's not exactly jumping up and down over the news that he and his wife Diane (Midler) have been recruited to babysit their daughter Alice's (Marisa Tomei) three kids when she and her tech-geek husband Phil (Tom Everett Scott) get a last-minute opportunity to have some out-of-town alone time.

As expected, uptight Alice's no-sugar-allowed helicopter parenting clashes mightily with Artie and Diane's old-school approach to child-rearing, not to mention the fact that Phil has programmed his smart home to be intuitive within an inch of its inhabitants' lives.

Also as expected are the resulting gags built around technologically challenged Artie. Fortunately, old pro Crystal comes armed with an arsenal of rim-shot-ready rejoinders that hit the mark more than they miss.

While his character has been given more of an emotional arc than Midler's (unsurprising, since the genesis of "Parental Guidance" came from a newly minted grandparenting experience in producer Crystal's life), it's still nice to see Midler strutting her stuff in her first onscreen comedy role in years.

And Tomei is always a welcome presence, even when she's saddled with what's essentially a one-note character for most of the film.

It would have been nice if director Andy Fickman ("Race to Witch Mountain") and husband-and-wife screenwriters Lisa Addario and Joe Syracuse ("Surf's Up") could have mined some fresher stuff from this frequently played ballgame, but at least when you've got Crystal calling the shots, you can still count on the occasional change-up.

"Parental Guidance," a 20th Century Fox release, is rated PG for some rude humor. 104 minutes.