Multicam using two sources of audio at the same time.

I have a 2 cam interview that used two lav mics, one for the talent and the interviewer. I dropped all the items into a multicam session. Is there any way to put both the lav mic audio files continuously playing in the multicam clip rather than just selecting one.

Yes, go to the "Switch video or audio separately" section on this page of the user manual:

help.apple.com/finalcutpro/mac/10.0.4/#ver23c76c9c

Another thing you could do is put only the audio tracks you need into a Compound Clip in the Browser. Then create a Multicam Clip from the two original clips plus the CC that has your audio.