Two clips I've found, that are relevant to our discussion of the contestants:
This one would seem to confirm that, yes, Contestant C was the Flight Lieutenant turned entertainer- note that the voice and (once aging is consider) face are the same.
This I'll leave open to the floor- our Contestant D (once we consider changes in fashion, the passing of around a decade, and the fact that her vocal tone may differ due to the audience), or not?
(And, as an actually-relevant point: If Contestant D is indeed the NYC-based children's show host, this almost certainly pushes the date of this program back to no later than April 1965.)