I'd be tempted to just sit down with him and do up a budget for the coming year. Be brutally honest, and then both of you keep a "spending diary" - you can start it off by going through bank statements for where things are spent, eftpos etc. Set up a common goal - a holiday or big spend (like a tv) and work towards that.

It is really hard, I find it hard to be brutally frank with my DH about money, but budgeting is a different thing altogether, and we are very aware of the need to prepare savings for our children. And to teach them about responsible money management - that could very well be the key to getting your DH to work out a budget - the kids are old enough to be involved in this as well, make it a learning exercise!