1 star

The 2015 comedy Dirty Grandpa paired Robert De Niro up with Zac Efron in a foul-mouthed hilarious road movie that played up the strengths of both stars, and gave both a chance to show off their comedic range.

While Robert De Niro plays Grandpa in this film too, the two films are in no way connected.

What a pity, because Dirty Grandpa was fantastic, and this film is, hmmmm, well, the best thing I can think to say about it is that is is 98 minutes long.

The War with Grandpa is a kids film, but just because it aims itself at a young demographic doesn't mean its filmmakers don't need to try. In fact, children are harsher critics than I could ever be. The other day, my friend's daughter asked me in all earnestness why I wasn't skinny any more and whether my hair was white or grey. See, they're brutal.

As the film opens, recent widower Ed (Robert De Niro) is living by himself and angry with the world. After an incident at a local supermarket involving shoplifting and the assault of a store clerk - at this stage the viewer can be forgiven for thinking this is the same character De Niro played in Dirty Grandpa - Ed's daughter Sally (Uma Thurman) intervenes and pressures him into moving into her family home to better support him.

To make room for Ed, Sally and husband Arthur (Rob Riggle) move their pre-teen son Peter (Oakes Fegley) into the attic and give Ed his bedroom.

Peter starts retaliating for the inconvenience, playing an ever-increasing scale of pranks his grandfather, and when Grandpa plays a few pranks of his own, Peter declares all-out war.

Ed warns his grandson that, having been in a real war, he knows they're serious things, and the writes out some rules of engagement for them to follow, including that the other members of the family will not be drawn in or hurt.

Grandpa brings in his old neighbourhood pals (Cheech Martin, Christopher Walken, Jane Seymour) to help with the feud.

Director Tim Hill has an impressive pedigree with family films, with titles like Hop, Alvin and the Chipmunks and Muppets from Space. These were fantastic films with great comic timing, hilarious on repeat viewings. He also penned the screenplay for The SpongeBob Squarepants Movie, also hilarious. So, I'm not sure what it is about this film that so badly fails.

The screenplay, drawn from the wildly popular kids' book from author Robert Kimmel Smith, has a lot happening, but not much of substance. Its writers, Tom J Astle and Matt Ember, have penned a handful of middling productions, such as the Matthew McConaughey flick Failure to Launch.

What might have provided decent fodder for fun scenes or caustic dialogue has been smoothed out by an apparent need to be offensive to nobody and appeal to everybody. Instead, it fails to engage either end of the audience range - pre-teens and the pension set - it aims itself at.

There is some marvellous talent on screen, squandered.

Sidekicks to De Niro are classic funnyman Cheech Martin and the always kooky Cristopher Walken. Not one laugh generated between them.

Jane Seymour appears as the love interest, and it is nice to see her back on the screen, but again, no great lines, no twinkle in the eye in her exchanges with De Niro.

This slate of classic film and television big names ought to draw audiences in, but the film's marketing doesn't share this with its audience.

Uma Thurman tries her hardest, but only Rob Riggle comes close to successful physical comedy.

This disappointing children's film kicks off the summer holidays, and its bland inoffensiveness makes it decent babysitting fodder.