Looked like an easy white kids circuit at Roche aux Sablons when we were there the other week.
Roche au Sabots had a really big kids circuit if I remember correctly and seemed like a perfect place for families. Is that were you were on about Slackline?
Has anyone tried the white circuits at Beauvais Telegraph? I'm taking the brother-in-law + 5 yo son out on Saturday, and it's a bit quicker drive from Paris.