This is always a difficult situation.
The reason is that children have a tendency to try to please the adults that they love and this can affect what they say if the adult is present and prevent the child from saying what they really feel.
I always remember walking past the office of a judge who had a reputation amongst the lawyers who used the court for being rude and difficult. The door was slightly open and he was swinging a boy round in his swivel chair much to the boys delight.
My point is that people who are used to working with children can put them at their ease and find out what they really think and want.
I hope this helps. If there are any further points please reply.