Concerning what animation movies for children will work we all have been terribly wrong at times. I doubt anyone has a perfect record of all successes and flops. Medieval settings, female heroes, dialect narrative: that could all be detrimental. But there are examples in the past that that need not be the case. At the moment I think Brave will do 225/400 DOM/OS with good European numbers.
It all depends on how children and their accompanying parents see those puppett-caricatures. They remind me a little of Asterix (french comic), but does Brave have this multitude of well drawn characters? The only thing we know is that it is about a rebelling princess. The Atalanta mythos comes to mind.