Have you read the book? There's only two situations, one involving a werewolf, the other a wizard battle, that weren't reproduced in the movie.
Everyone around me jumped at one scene, and we ALL knew it was coming.
(They had a trivia contest beforehand and the competition was fierce, lol. Very knowledgeable group.)
There are a few scenes that could startle skittish kids and leave them with a fear of drowning or falling. Not to mention the "snogging" (making out) that pervades the movie - he might not be interested, lol. (My kids yelled out "Face Suck!" -- we made them stop immediately, of course.)
I wouldn't take a seven-year old. When my kids were young, I let them watch it on TV/DVD, but not on the big screen.