I've been there twice. I don't think bringing children of your childrens ages is a problem, and your girl will probably enjoy it very much, but your boy might be very bored.
You'll see very few men (I get my husband there only because he can order a beer instead of tea).
It's a frumpy, frilly, flowery environment, and your son might be "ewwwwed" by that at his age.
But then again he might really enjoy it.
I don't feel that babies, toddlers, and preschoolers belong at this event, but older children are fine, although I think a lot of them might be bored. Only you know them well enought out make taht decision.
It's a wonderful way to spend a relaxing hour or two, and you'll leave stuffed, so be prepared!
Anne