Your fields look great, Derek! Critters must be liking them.
Just a thought ...... if you want to let some taller cover for fawn security, maybe let it all go until you get ready to seed brassicas into it - then mow or roll it down on top for moisture-holding mulch?? AG guys know more about this sort of seeding timing / mowing / rolling stuff. We've done that same thing (seed-then roll) with a field of buckwheat with good results. Also a field of rye & clover, over-seeded with brassicas - then mowed. FWIW.