I want to use a 12yo girl with down syndrome as main character. Trisomy 21 people has a low IQ, normally around 50, at least according to Wikipedia.
I've known a few people with such syndrome over the years, but never so well that I could rely on what I know from them to create my character so, the most obvious choice would be Forrest Gump, since I don't want the character to be too much dependent (and one thing I can say about the Trisomy 21 people I knew, is that they are dependent but not that much that the couldn't handle themselves in normal daily tasks, on the contrary).
The problem is that I don't want the main focus of the story to be the character struggle against his impairment. It's not a drama. The girl will share the plot with another main characters and I don't want to develop her in such a deeply way, because of the book size.
I think it's easy to fall into clichés and I don't want that also. I want her to a believable character who is facing a really complicated situation with others that can help her in the same way they would help a 12yo normal child but, of course, will underestimate her because of the problem she has.
So, my question is, did anybody work with such characters? How you managed to escape the cliché problem?
(btw, just tell me by the comments if you think this question does not fit here, and I'll delete it)