I would go with a lightweight blingy something or other.
One of the girls I used to watch (and still do occasionally) has that sort of style and big bows would weigh it down I think. If only the top half of an alligator clip is lined, it should still slide in.
If all else fails, ask the mom what kinds of clips work in her hair ... although now I think about it, the mom for 'my' little girl never even thought of hair accessories until I brought up the subject.
Good luck with the shoot and let us know how it goes!