Who is choosing / paying for your USA trips ? Is cost a factor ?
What is the timing is the flights above ? With young kids I would be looking to reduce travel - layover times.

You do not always need to fly a specific airline to get its FFP status. Subject to the FFP t&C's you can get status on any OW airline (especially in J)
A lot of kids have high AA status. AA SWU's are worth a lot (but use on MH or CX)
MH status is likely to be little use to you in 4 years time

AA best in my view (considering your 4 planned years in Asia)
Worth noting that Qatar QR join OneWorld some time in 2014 and are an AA partner airline now

Have a look here: http://www.flyertalk.com/forum/onewo...help-here.html

Edit:
Link to your question in the *A forum http://www.flyertalk.com/forum/star-...asia-base.html