L.T.
Here is the link to the TSA web site with the most recent information regarding traveling with breastmilk:
http://www.tsa.gov/travelers/airtravel/children/formula.shtm
I don't think it would hurt to call the airports and/or airlines prior to your trip just to confirm that you can bring your pumped milk on the plane, but it looks like the regulations have changed with respect to breastmilk.
Also, here is some information about how long breastmilk "keeps" in various situations:
http://www.kellymom.com/bf/pumping/milkstorage.html
Here is another list of tips that popped up when I did a Google search for traveling while breastfeeding:
http://glenniacampbell.typepad.com/silenti/2007/05/unacco...
I'll be doing the same thing in October, except my baby will be 11 months by then, so I've been thinking about how to do this as well. Good luck!