HTTYD, thankfully, doesn't placate kids. It's not a situation where the kids are smarter than the adults in the film. The dragon that interacts with our hero is a playful, emotional animal. It never talks, but is still able to communicate in a typically animalistic way. And there's plenty of high-flying dragon-riding action to be had, but the dragon antics have a sense of weight and scale and urgency.
In other words, this is the movie Eragon wishes it could have been.
The characters have a lot of heart, the dialog is curt and snappy. There are a couple of shots that were clearly designed to milk the 3-D and play around with focus. But honestly, I saw the film in 2-D and it was just fine. And there are plenty of jokes for adults, there were quite a few moments were my friends and I were laughing raucously... alone (one particular joke about a breast-plate stands out in my mind...).
The movie never got overly preachy, and when it came to the hero's plight, real choices and real sacrifices had to be made. And that's refreshing. And Abby would chastise me if I neglected to mention the quality of the animation of, particularly, stubble and fur--very impressive. So if you get a chance, take the kids to see How To Train Your Dragon.
Because it's way, way better than the last Shrek movie was.