I'm not surprised, younger children may find three days of any kind of music a little tedious. However, on Saturday afternoon a childrens entertainment will take place at the top of the main field. In the past, this has involved learning circus skills, improvising and performing a play, chasing around after huge inflatable objects, and goodness knows what else. Despite clear evidence that I am entering my second childhood, they never let me join in, so these observations are based on passing a pack of costumed, painted, overexcited screaming kids... but they seem to be having a good time.
If your children are too old to accept the title children, and you're worried that they won't enjoy the Festival because every time you play your music at home they beg you to "Stop playing that old rubbish" - bring them. They will love it. They won't be uncool enough to tell you so, but they'll be desperate to come back next year. You can safely leave them to wander and make new friends. It is entirely possible that you will hardly see them all weekend, until they run out of food or cash. Here, I do speak from experience, having taken a strategically shaved and pierced lover of nu-metal to Cropredy (the child of my partner, before any suggestion takes root in your mind).
Whatever type of child you bring, organise a meeting place in case anyone gets lost.