IMHO only!
- If he enjoys reading them, he understands enough. (And if he doesn't, so what?)
- If both of you enjoy him reading aloud to you, go for it. If not, why make an otherwise-enjoyable experience a chore?
- If both of you enjoy you reading aloud to him, go for it. If not, why make an otherwise-enjoyable experience a chore?
I personally hate reading aloud, and don't enjoy being read to, so I was glad when my DD preferred reading her own books to her own self.
MTH roughly increase in difficulty and length as you go, so that's a consideration if the lower-numbered books are at the edge of his comfort zone. IME, there is not a significant difference in difficulty between books within half a grade level of each other.
The older ones tend to come in sets (so 3-4 books go together to make up one extended adventure), but it's more "Book 2 recaps some of the plot of Book 1," and not at all "Book 2 is unenjoyable for those who haven't read Book 1."
"My kid wants to read them in order," IMHO, is an excellent reason to read them in order.
