It may help if any infection is present as a burden to the body but you can't overlook deficiencies or toxicity of some kind and Miracle-Mineral-Supplement may not be the best way to deal with it though it is claimed to help with mercury.
Candida in a child is best dealt with by diet and avoidance of Antibiotics .
MMS doesn't seem to be the best to deal with this. Alternatives are coconut oil, Colloidal Silver , zapping and Iodine supplemenation