La Petite bande (1983)
Directed by Michel Deville

Film Synopsis

A group of young children, aged between seven and ten, have had enough of their boring, uneventful lives in England.  They have a taste for adventure, so with their modest stash of pocket money but no end of enthusiasm, they scramble across the English Channel in a pilot boat and are soon discovering the delights of la Belle France.  It isn't long before this happy band of boys and girls are making the most bizarre encounters, including a musical dog.  It seems they have arrived in a fantasy world where anything is possible.  The biggest surprise awaits them in a haunted castle lost in the depths of an enchanted forest.  Here, some incredibly nasty folk have invented a device that can force children to become grown-ups against their will.  How is our intrepid gang of heroes to escape this terrible fate?  The answer lies on a mysterious desert island...