The Goonies - great movie for kids - I wouldn't classify it as horror but for kids it is scary with a monster in it. Might be just enough gruesomeness without blood and such. If you don't want to get scared might be just right.
Buta if you want something geared a little older - try some PG-13 should have the right level of horror without being too strong. I did a quick search for PG-13 horror movies and got this...
I haven't seen those other than Signs and I think that might work - it has some funny parts as well. Another Sixth Sense, I believe is PG-13 - not listed here that I have seen. Some one also mentioned Poltergeist which falls in that rating.
another - not in the horror category but would be good for that age I love is Stand By Me.
If you don't really want true scary - I would suggest Stand By Me or Goonies. If you want scary, but not over the top then somethink like Sixth Sense, Signs or Poltergeist.