I don't think you need to wait until age 11
This film is scary at points, but the monsters in this film aren't much more terrifying than, say, scenes in Ratatouille in which Remy is attacked with a shotgun, and are a lot less realistic. The film has important things to say about fear: that the things that scare us are the things we don't yet understand, and that the way to overcome fear is not besting opponents, but getting to know them. Maybe in the theater the monsters would be too intense, but I think on DVD a 7-year-old will be able to stay with the film long enough to see how the little girl learns to overcome her fears, which renders the monsters a lot less scary. The parents' behavior at the top (gorging themselves on food in an abandoned shop) is a little troubling, parents could explain to kids that a magic spell is causing them to forget their manners (this is actually the case, but the magic is not apparent until later in the film).