Moscow is a fun and happening place to live and there's plenty going on for families too, from expat groups to some great children's venues. Try:
www.childreninmoscow.ru - for family- and children-related information
www.livinginmoscow.ru - for all general Moscow information and to subscribe to Barbara Spier's "Fun Stuff" mailing, as well as order a copy of her excellent relocation book
www.bwcmoscow.co.uk - the British Women's Club
www.iwcmoscow.ru - the International Women's Club
www.awomoscow.org - the American Women's Organization
www.redtape.ru and www.expat.ru - expat sites with forum sections
The main issue of where to live depends on where you/your dh will be working and where your children will be going to school, as the traffic is terrible for commuting. The main international schools are the English International School (to the East), Anglo-American School, International School (to the West) and British International School. If you like going out and seeing/doing things and you don't mind pollution then it's probably better to live in the centre. If you don't mind living in a compound community out of town then you've got Pokrovsky Hills, Rosinka and Serebryanny Bor as the main out-of-town complexes.
Rental prices (and costs overall) are generally high in Moscow although there's more room for negotiation now that the crisis is here, so you should be able to significantly bring down any asking price (some landlords are very greedy and stubborn, though!). Your company or relocation agent should be able to provide you with more information and possibly negotiate on your behalf. Barbara Spier works for Allied Pickfords and her relocation book, Living in Moscow, is considered by many expats to be a lifesaver; the new edition is due out this month so you should try to get your hands on a copy.
Joining the expat clubs and going along to their open coffee mornings will help you settle in. The BWC has an active Family Network and the IWC runs a children's group. There are some privately-run groups listed on the Children in Moscow website as well. Going to school/kindergarten will also help both you and your children make friends.
I think that's about everything in a nutshell!