hello, my ears were burning 
(formerly mumoverseas)
as laptopwieldingharpy said, I lived there for 5 1/2 years and moved back to the real world/UK last summer.
as kilmuir says, women cannot drive and have to wear an abaya (and headscarf) when off compound.
I lived in Riyadh which is probably the most strict of all towns in KSA. Dhahran is far more relaxed and lovely as nice and close for weekend escapes to Bahrain. Do you know where in KSA your DH would be?
Hopefully your DH's company would provide accommodation in compounds and if so, that will be a nice lifestyle for you and the children. I certainly wouldn't want to live in a villa outside a compound, far too restrictive.
The compounds I lived on had fabulous facilities. The last one had indoor and outdoor pools, tennis courts, sports centre, gym etc. A small shopping centre and a few shops restaurants. It is very restrictive though. You sacrifice your independance for the money.
Depending on your husband's package you may get a houseboy (cleaner) - they are called houseboys and are proud to be called that buy some people (normally british people who have never lived abroad) seem to get upset about the job title. Also, depending on the package you may get a driver and school fees paid etc.
My DC went to the British International school there and I have to disagree with Kilmuir in that think it was better than some schools in UK. The class sizes were much smaller. In foundation 1 (year before reception) they had a maximum of 20 in the class but in reality there were normally only around 16 and then the rest of the years had a maximum of 24. You would need to make sure your DH's package covered school fees as otherwise that could get expensive.
You would also need to make sure that you would be able to join him in September. Unfortunately the old company that DH worked for always made false promises telling men that their wives/DC could join them in 3 to 6 months but in reality there was a waiting list which could be up to 3 years. Your DH is in a good position to negotiate before he goes, so make sure he checks out all these things.
Of course it does get very hot in the summer, it is in the middle of the desert. Most wives/DC tend to return to the UK for most of the summer as its not much fun there.
I assume you know its a 'dry' country, ie no alcohol and no pork.
If you want any more information or have any questions please feel free to PM me.