set up a seperate account for things like rates and rego/insurance. you'd be surprised at how much they can cripple you when they come.doesn't really make any difference what you do in the future, budget for how things are now (so car loan and rego on existing cars - better to budget for it and not need it then vice verse kwim)
set up an play fund for things for the girls - outings, clothes etc - and don't blow that amount. if you can't afford to go to a play centre out of that amount then change MG to someone's house.
if you're planning on buying bulk formula, still put that amount away each week (or however often you need it) so it's there waiting for you, not money you have to come up with