If You're friend uses Pro Tools, give him a small Quicktime, so he has a visual reference while mixing.
For the real audiomix give him an OMF file.
Use Export OMF and give a handle lenght, usually 1 or 2 seconds will do.
I don't know about iDvD, but I think you want to create a Data DvD and not a Video DvD wich I think iDvD will create.
I use Toast as burning software, but in finder you can create Burnfolders
an burn those.
Is This Any Help
Crisp