I haven't seen Quidam, but I have seen four other Cirque shows: Saltimbanco, Alegria, Dralion and La Nouba. I would say that none of the ones I saw have scary parts in them. Each production is absolutely amazing and beautiful, and the performers are unbelievable. If you can afford it, definitely go and see Quidam. I'm sure you won't be disappointed.
warmly,
claudia