Dear
You need to consider the following
1.Rent
2.children schooling
3.other monthly cost
Rent is gonna be main part of ur cost u will get decent 2-3 bedroom apartment (fully furnished) for a cost of 7-15K depends on where u stay
Children schooling can cost u 30k-50k per year
Stationery,food and other monthly cost may be between3-5k
Apart from this u need to also plan to buy a car as public transport is not so great
Also remember as per Qatari law ur also entitled to one month salary (basic) for each work year once you leave Qatar ( end of contract)
What about yearly return ticket? It's not clear from your description
Does ur company provide initial luggage move ?