Here is what I think... the offer is so so (if yo uare American with qualified degree).. but it is ok.. perhaps you can negotiate a bit. Bear in mind that you may be able to save a bit more but you will have to give up on the quality of life. Also you need to look into taxation.. there is no point to move if you would still owe taxes to US Government. There might be some other benefits that the company is able to offer you.

Now regarding your assumptions:

Rent 12k allowance - i think you can ger a decent 2 bdr apt for about 8K or so... but if you want to live in West Bay where most of expats live you will need 16 k.. i dont recommend living in West Bay thoguh... it is not the best value for the money

Gas 250 - yes

water 300 - roughly correct.. may be less

Power 300 - yes

Mobile 300 - depends on you.. but may be

Mobile2 300 - - see above

Internet 500 - no... 220.. but if you want ultrafast then 320

Auto Loan 5000 - better buy a used car than take a loan if you can .. also the ocmpany may offer interest free loan

Auto Gas 500 - more like 300

House Maid 2000 - about 1500

Grocery/Lifestyle 3000 - grocery for 2 adults and 5 kids is about that.... then you need to add lifestyle which really depends on you... bear in mind both rent and food are more expensive in Qatar than US

My advice.. find out more about taxation and do negotiate with the company.. if you are more of on a junior side (less than 10 years experience).. then the offer is fine.