An artists' playground opens in the grounds of Sudeley Castle in Gloucestershire this week. The opening of this annual sculpture show has become quite a fixture of the art world's summer calendar, and this is its most ambitious one to date, and its theme is play and recreation.

Outdoor sculpture is a competitive field. At this time of year, contemporary pieces pop up in the grounds of Britain's “statelies” as profusely as cow parsley from the verges that lead to their wrought-iron gates. Relative newcomers, such as Mount Stuart, Narborough Hall and Compton Verney, have joined such established sculpture parks as Goodwood or Roche Court, and it sometimes feels as if there's barely a big place left in Britain that doesn't have plans for its own sculpture fest.

Of course, Chatsworth sets the standards as it teams up with Sotheby's for an annual show. But Sudeley, taking the rival auctioneering house of Phillips de Pury as its partner, puts in a firm competing bid. It has plenty of potential. Sudeley Castle, a charming confection of Tudor history and honey-coloured stone, folded into the contours of a gentle Cotswold valley, has a lyrical romantic beauty - despite the Victorian additions and the absence of a duke.

Its play-themed exhibition this year is a relevant idea. The boundaries between art and entertainment can often feel blurry. Postmodern play has turned into high culture. It can be hard to know the difference between philosophy and fun.

The contributors offer a broad range of takes on the theme. Among the 15 or so featured artists you will find a handful of big international names, a scattering of home-grown talents as well as a few exciting up-comers.

Here, for instance, is a paraglider-style flying contraption created by the Belgian-born Carsten Höller (probably best known for his helter skelters at Tate Modern). The spectator becomes participant as he straps himself in, feels his earthbound perspective on life slowly vanish as he is carried off in slow airborne circles like some cumbersome bird. But here too is Michael CraigMartin, the godfather of Brit art, making a huge pink garden fork. It sticks in a slope, as if some giant Gardening Barbie has just left it. It's called Pitchfork. “But it's a garden fork,” I point out pedantically. The artist nods ruefully. “So I've been told. I called it pitchfork because it was pitched at an angle,” he explains.

Here, too, is Kevin Francis Gray's The Hanging Tree, in which a girl in a long white veil sits perched on a high cedar bough. I don't want to spoil the surprise, but the peacocks that roost above her, with their long veil-like tails and their slow mournful shrieks, set a suitable mood. This eloquent attention to the setting is one of the main points of taking a show out of the gallery. Jonathan Monks, for instance, makes an artillery cannon. But he is an artist known for making fun of the artistic canon. And where else could this pun work better than when wheeled out in front of a castle that is staging a contemporary show?

The show is not entirely successful; it's a mixed selection. The most appealing work was by Henry Krokatsis. A gothic pulpit coiling around an oak trunk, as religious constructs have coiled around the tree of life, seemed a simple but effective conceit - not least in the light of the fungi that flourished alongside it. And a further piece in the chapel felt equally apposite.

Perhaps the lesser-known artists try harder. This year's show had a strong design element, courtesy of the design dealer Kenny Schachter, who apparently helped to co-ordinate the show. But for all that Zaha Hadid is so famous, her contribution - a funkily self-conscious slide - looked rather like an old car radiator grille left lying amid the dying grass.

But then there will always be a handful of pieces that leave the visitor baffled and wondering why the artist even bothered. (In my case it was the works by Ai Weiwei - a cluster of unremarkable pillars - and Lawrence Weiner, who contributed a pair of conceptual plywood boxes on the pond.) But perhaps this lack of engagement, as much as any excitement, can serve a purpose. It can lead you to focus on your surroundings anew and perhaps see more freshly. At Sudeley there is much to enjoy. If you don't see the point of the artworks, look at those vast crimson poppies. Everything in the garden is perfectly lovely.

The Artists' Playground, at Sudeley Castle, Gloucestershire (01242 604357), until Oct 31

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