Taking into consideration the info provided, your husband can expect a minimum package of 8000GBP per month, plus housing allowance (could be around 2000GBP per month) (if the company does not provide a Villa), plus family health insurance, plus family air ticket once in a year, plus 1 month paid vacation, plus Car allowance for a decent 4x4 (if the company does not provide a 4x4 Car), plus annual gratuity of not less than 3 weeks of Basic Pay, and possibly Children's Education for upto 2 Children.
In addition to above, the company should also pay one time relocation allowance, annual furniture allowance, etc.
You may consider Utilities & Fuel allowance included in the 8000GBP per month, as it does not cost much in Qatar.

You can start the negotiations with this package and slight addition/deletion should be okay.

Also, try to have as maximum as possible as "Basic Salary" out of 8000GBP per month, as the Basic Salary will be the basis of counting your annual gratuity upon end of services. Sometimes the companies allocate a very little amount as the "Basic Salary" and show the balance salary as different types of confirmed allowances, to save the gratuity.

Please keep in mind that Qatar needs hundreds of thousands of qualified & experienced professionals in the coming months, so if this Contracting Company does not offer you the desired package, you can still expect the same package or even the more from others soon. Keep an eye on the adverts and keep sending your CV to the HR Consultants.

Albeit the quality of life is better in UAE, but there is a job security in Qatar, and you will soon start loving it.

All the best !!