Update since I first posted. I racked from well under the floating buttons to two one gallon containers. On the recommendation of my LHBS, I left little headroom and repitched with RED STAR MONTRACHET yeast and FERMAID K. The ensuing vigorous ferment glubbed up the airlocks (which I replaced with a clean-one 3 times) but insured a blanket of CO2. They're still going and no moldies detected.
One of the things I learned in the process are that yeast for Mead must have a nutrient cocktail from the start to get things 'rolling'.
I'm already planning my strategy for another batch next month.