those 7250's will not play wavs
Check this LINK
to see which handhelds support which audio codecs.
As of now though there is no support for the ability to play wav files within emails. There will be support once handheld software 4.2 comes out from rim. (In beta stage right now) Even still, 8700 / 8100 / 8800 will be the only ones that it will work on.
Check this thread
for updates on when the 4.2 OS will come out and other issues.
Also, There are a couple of third party apps out there that convert the wav files into basic text for you. I haven't looking into them too much though.