as a person with first degree in educational and developmental psychology, I would say that children till age of 11-12 could have difficulties to fill in their asnwers without help, i.e. you need one-to-one contact, where you ask them questions and record asnwers yourself. In addition, questions you will ask to childen and somebdoy with univ degree definitely will be diferently formulated. because, if you ask a question that an 8yrs old understands to somebody with BA, they will think you think that they have intelctual development difficulties. either you find a creative approach how to design surveys for all groups so that they understand& can fill them in & dont feel offended OR as you said- need three slightly different questionnaires studying the same phenomenon, just questions are phrased according to the understanding of the group.