"I would use ULF film and do contact prints from them...
Any ideas on how shallow the DOF on the lenses are?"
Not much, at 11x14 or larger, portraits would be at 1-1 or closer. Another bother would be the process lenses for these cameras are optimized for flat-field works (no DOF) and standard lenses long enough are rare and expensive. 420mm or longer should work well and give enough distance from the sitter not to scare them too much.
Have fun with it, sounds like a fun project.