My impression of Kumkn is that it's less actual tutoring & more self-paced work through a very structured series of work books, as such it favors advancement in maths over language skills. I nearly strolled into a tutoring job with them with no quals other than good HSC scores - that's not really the sort of skills your child needs from a tutor. If there is nothing else at all in your area, well, maybe try it. But if you can find someone else to provide one on one or very small group learning support, then get them.

Retired teachers make awesome tutors. Sometimes teachers at the school provide additional tutoring, so it's worth asking about that too. Also ask around - ask the OT and other parents, keep asking until you find someone.