Rent and schooling costs will be the most expensive things to worry about. Getting your kids into a good international school is even more of a headache than the fees. Most decent schools are already filled and have waiting lists.
I believe there are other threads/links on here that can give you approximate housing and schools costs at various places in Doha. But as I said, it won't matter how much things cost if you can't get your kids into a good school. I suggest you call schools directly and find out if there are even any openings. My guess is there aren't any at this point.