THE CHILDREN, a British horror film about murderous -- wait for it -- children, may not have many surprises up its sleeve, but surprisingly adept execution and plotting keep it from devolving into derivative schlock.  The story follows two families that have gathered at a large home in the snowy woods for fun and frivolity.  Unfortunately, the tots start to vomit (vanilla pudding, it would seem) and then come up with some games that happen to be fun even AFTER someone loses an eye.