I would definitely agree that you need buy in from your DC. If the client sees nothing to be gained from therapy, that is exactly what you will get.
I also always encourage my adolescent students (and this would apply to GT preadolescents as well) to
1) reflect on what is most important to them as goals of therapy;
2) articulate these goals for any prospective therapist (and your parents);
3) remember that you are the customer (i.e., advocate for your own felt needs); BUT ALSO,
4) be open to additional goals that might be suggested by people who know you and wish you well (e.g., your parents).
If you and the therapist cannot develop clear communication on the goals of therapy, and how you are working together to achieve them, then this partnership is not a successful one (not that this is a poor therapist, necessarily, or that you are an intractable client, but that it is not an effective combination), and you should cordially say your goodbyes and move on.
And I emphasize that I am having the same conversation with them that I would with an adult, because they are self-aware and personally responsible enough not to be treated as powerless small children.
