Back to the drawing board - My new wondering

As mentioned earlier my Manaikalani COL inquiry wondering was "How can I use Developing Mathematics Inquiry Communities (DMIC) pedagogy to develop the vocabulary of my kids? The focus was on developing my kids general vocabulary using DMIC maths.

Having done some research into vocabulary development I have since decided that trying to develop general vocabulary requires different pedagogy to that of  DMIC maths. I was also challenged by Dr Rebecca Jesson to think more about the problem I'm trying to solve before I think about how I'm going to go about solving it e.g vocabulary development pedagogy or DMIC maths. This was great advice and I have now identified the problem I wish to inquire in to.

PROBLEM: My kids struggle to explain and justify their thinking and reasoning in maths.

In fact the struggle to do this in other areas too however it is particularly poor in maths (my hunch is if it improves in maths it will also improve in other areas). This lead me to a new wondering. 

WONDERING: How can I develop the mathematical dialogic discourse ability of my children?

This year I will be endeavouring to find a solution to this problem. Any thoughts/ideas you have on the matter would be greatly appreciated.