I've read the 'In Event of Moon Disaster' transcript, to be delivered by President Nixon in the event of Armstrong and Aldrin being stranded on the Moon, but have a few further questions:
Was this speech to be delivered whilst the astronauts were still alive?
Would NASA have ended communications with the astronauts while they were still alive?
How would the astronauts have died? Would they have waited for the the oxygen to run out? Would they have "vented" the oxygen out of the lander?
I assume there weren't any plans to recover the bodies on a later mission, due to the logistics and having two dead bodies in the capsule on the way back to Earth. Am I correct?
The plan was, once it was obvious the astronauts were beyond rescue, for NASA to allow the astronauts to record a final statement for their families and posterity. NASA would then end communications and allow them privacy in their final minutes or hours.
The astronauts would have been allowed to decide what happened next. The method of death would be their decision. They likely would have shut off the flow of oxygen - that would have been relatively peaceful. I don't want to speculate too much on that.
There were no plans to recover the bodies. I think it would be very unlikely that any such plans would ever be devised.
Source is William Safire, the White House writer who devised the contingency plan and wrote the speech.
I don't have the book on front of me at the moment (posting from phone), but Jim Lovell (of Apollo 13) and Jeffrey Kluger actually addressed the suicide issue in "Lost Moon: The Perilous Voyage of Apollo 13"
Long story short: the astronauts would not take suicide pills. The quickest, easiest, most painless way would be to simply open the hatch and vent the atmosphere into space. You'd pass out in a matter of seconds, after which you're done.
William Safire was one of Nixon's speech writers, and wrote the famous speech you cite. In his autobiography Before the Fall: An Inside View of the Pre-Watergate White House, Safire states that death would either come from eventual starvation or dehydration or "deliberately 'closed down communications,' the euphemism for suicide." The method of how is not detailed, likely such a personal choice would be left to each astronaut.
To provide a historical context that such a disaster was a very real and well known possibility below is a link to a radio play broadcast on a science fiction series in 1956 with a similar story - it's an orbital mission, not a lunar, but covers the same ground:
Many more episodes of that and other old time radio series are available on archive.org if you enjoyed it: