Assuming that you've put the LAN wired and wireless networks on the same subnet, yes - there will not be any problems.
As I mentioned however, if your Mac is on wireless, bear in mind that the streaming actually happens via the Mac... so with your network configuration, the data will be pulled from the AEx HDD by the Mac using wireless, then streamed out to the PS3 back via wireless and then wired. Bearing in mind the very low-end aspect of the networking hardware involved, I'm not absolutely sure you'll get smooth video. Still, Medialink is a good solution and if you have doubts you can try it first.
Medialink basically emulates a dlna server on the Mac side, so that the PS3 can pick up the iTunes library as the source. Anything which is generally formatted for iTunes and iPod, the PS3 should be able to play - although you may need to play with some of the files.