Emma,
EFT is a wonderful therapy for children and adolescents with learning difficulties. It can be used on a wide variety of emotions and limitations related to the disability, such as fear, anger, frustration, shame, rejection, lack of focus, and the limitations in general.
There really are no cautions. Honor where the child is and work with them. As you learn the technique I would suggest using it along with them, if they can not follow it, that is OK, it will still work with you working on it. I am sure that you will find it amazing.
I am anxious to hear other input from other practitioner's who can share examples of their successes.
I wish you well