Ok, so since you are thinking that starting with CM now would be what is best, I’m going to say that is what would be best because you are his mother and you know what would be best for your child!
I’m not really sure where’d I’d go with math if I were in your shoes. Does he have all the basics down pat? Addition, Subtraction, Multiplication and Division. If not, I’d start there for now.
Reading is easy. Pick a book he’d be interested in, have him read a chapter a day, and then tell you what happened in each chapter. I wouldn’t worry about written narrations just yet, since he’s just getting started. I’m not sure what reading level he is at, but my 5th grader is loving Chuck Black’s Kingdom Series. Tons of adventure and biblical allegory.
For Science, I’d do nature study and a living book for now. The free curriculum guide has a list of living books in the science section. Pick one that would interest him and have him read and narrate. For nature study, we’ve been going out and writing down and recording the “firsts” of the season. So when we notice that the tree frogs are back, we record that. The first time we saw that the lilac bud, we recorded that. When the first daffodil started to peak out of the ground, we recorded that. That’s an easy way to start nature study for now.
I suppose for History, you could figure out where it is you would like to start. Are you planning on using the SCM guides or Truthquest or someother guide to help you navigate what to teach? If you are, both have samples. You could figure out which one you plan on using, and look in the sample pages to get started. That way you don’t need to wait on starting history while waiting for the materials to arrive.
Hope that helped!