Bumping up the ages takes away some of the impact of the story, but it's necessary if you're going to make a movie. You're just not going to get child actors that age who can carry that kind of material convincingly.
I'm definitely curious about this, if only to see how they do the battle rooms. It's one of those things I had a hard time visualizing in my head when I was reading the book.
"COLONEL KLINK, WHY HAVE YOU FORSAKEN ME?!"