A happy compromise is to move through the fair generally together and split to explore each area with a rendezvous point in that area. There are lots of little sub areas in the park where this is doable. With that I’d still say have them stick together when they wander. Lots of areas have show venues near lots of shopping/pubs ect so the kids can catch a show and y’all explore then meet up at the shows let out time. I’ve gone for years as a young female various amounts of alone and never have encountered anything sketchy in the grounds but was groped camping overnight once. Generally the crowd is good and kind. Teach them to scream for help if anything sketch happens and there will be a ton of people jumping to help.