Keep in mind that, while the PJ2 has standard headphone jacks, the audio output is STILL listed as 8 ohms, rather than the standard 150-300 ohms of the aviation headset. The standard headset will work, it just means the audio output will be ~6 dB lower. See page 27 of:
http://www.sportys.com/media/pdf/newpj2manual.pdf
Depending on how loud the mower is, the volume to a standard headset may still be adequate.
It's really kind of funny: General Aviation is the only entity that HASN'T switched to an 8-ohm standard. US Military did so in the '50s, but our headset and microphones are still compatible with the 1920s telephones they were derived from....
Ron Wanttaja