i didn't order mine online, i got mine a few days before the show at the ticket office when we went exploring dtd and the west side. i was lucky and was able to get a great seat and was able to choose it. i DO think you can pick your seat though, or try to. i know a little seating chart does come up when you are online. maybe that could be just for the sections or rows. but if you really want to check the availabilty...you maybe should try to call for tickets instead of going online.
one tip though is that you don't want front row seats. a lot of the performance is in the air and there is a pre show -- if that is what you want to call it -- that takes place on the mezzanine walkway.