I was set to interview Keith Allen in the run-up to Treasure Island, but he cancelled. I mention this non-event because, Allen not being someone I naturally associate with children’s entertainment, my central question was going to be: “Who’s the target audience?” The poster gave little away. Was it even to be a kids’ show? Would it be dark and/or adult? And how would he be playing Long John Silver? Straight-up murderous or loveable rogue? Having seen the show, I still don’t have my answer. What’s more, I’m not sure the production team has it, either.

With Sean Holmes at the helm, Ken Ludwig’s re-hash of Stevenson’s classic swashbuckling yarn seems incapable of deciding quite what it wants to be. The rather mundane script is too serious for its largely frivolous delivery; the music (on-stage, for no evident reason) sounds like out-takes from Madness B-sides; and despite the extensive use of audio effects and video back-cloth, there is really no discernible atmosphere of any kind.

The production opts instead for glimpses of everything – musical, epic, comedy, panto, ballet even – but with no one mode sustained for more than three minutes at a stretch. The end result is inevitably scattershot, like bad kids’ TV (I spent the entire show braced against the possibility that one of the Chuckle Brothers might suddenly appear, parrot on shoulder: “What’s that, Cap’n Flint? Someone’s cut the hawser? Oh deary me . . . ”), to the detriment of even the good performances.

Allen is entertaining as Silver, but – under direction, I assume – he’s not nearly nasty enough. Ludwig et al. have knocked the edges off Stevenson’s morally tricky character in order to exaggerate a father-son proxy bond between Silver and Jim Hawkins. At his black-hearted worst, he’s no more frightening than a prep school rugby coach.

As Blind Pew, dishing out the black spot, John Lightbody was really, effectively unpleasant. Unfortunately, he was also camper than Richard O’Brien. There was, in a general, way too much pawing at Jim (Michael Legge) by almost every male character. If this was supposed to be funny, it tanked.

Favourite credit goes to Matt Costain, Director of Rope. He was responsible for some of the more eye-catching stage-craft, including his own acrobatic death as the wonderfully-named Israel Hands (Ezekiel Hazard’s not bad either). And Paul Brennan elicited sympathy for the maroon Ben Gunn, if only by playing him as a comic, cheese-fetishist Caliban. Quite where Gunn (or anyone) would have picked up a Scottish-Jamaican-Kazakh accent was more of a mystery; but by the time he appeared, this blatant foolery was just what the show needed. Hesitant though I am to endorse panto, it should perhaps have been the default setting.

Whether or not Treasure Island is really aimed at kids – and I guess it must be, if only through process of elimination – they do get in half price. If you think yours will love it, though, book soon; I don’t fancy its chances of making it through to the February half-term.

Treasure Island is at the Theatre Royal, Haymarket, until January 3 and February half-term. For tickets, priced £20-£45, call 0845 481 1870 (www.treasureislandtheplay.com).