Any age can go to Scarowinds. You can opt out of going into the haunted houses/mazes, but people in scary costumes do roam the park. You can purchase, for an additional cost, a no scare light up necklace to tell the Scarowinds personnel not to scare your child. I think they are $10 and called No Boo necklaces.
Scarowinds happens from 7 pm until midnight. The regular park hours don't do the scary stuff. They close the park at 5 pm and then reopen at 7 pm for Scarowinds. There is an additional fee to go to the later event and I believe there is an age restriction for Scarowinds.
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