I've just finished a six wk course with my 2 yo twins, at the Childrens Centre. It's called 'Talk and Play' and we were booked onto it following a 'Well Comm' assessment they did.
It might be worth getting your DH to drop into your Children's Centre and see if they offer the assessment / course, or anything similar.
The course has been great for my two and there were lots of handouts with info about helping their speech.
In the sort term, one thing that really helped mine was to speak slowly and clearly, in short sentences.
So instead of me waffling at them,
'Come on, it's time to get Ds 1 and 2 from school now. Lets go and get our shoes and coats on, it's a bit cold outside, looks like it might rain', blah blah
Just say,
'Time for school. Where are your shoes? Coat on.'
That kind of thing. Let him hear the words that matter and try and try and cut out the waffle around it.