Convert .mxf files with High bit rate and multiple audio channels to smaller files +keep audio chans

I have large .mxf files that are at an unnecessarily high bit rate but with at least 8 channels of audio. Is there any way I can make these files smaller (H264 .mp4 would be fine) whilst also keeping the audio? I'd love to do it in Media Encoder as a batch if possible. 

Thank you in advance for any help you can give.