The problem with a zafira is that their a great motor but when you put the back row of seats up you have no boot whatsoever,which is a pain.
Galaxy does everything better really with the vw pd tdi in it,which is the best diesel of that generation.
Merc ml's are getting cheap now but beware that when they break (which they will) they do get expensive,and no more than 30mpg in derv form but drive nice and plenty of room for the kids,good safe motors too.