Powerline Adapter Into Cheater Plug
The adapters that you purchased should be unaffected by the so called "cheaters".

Power strips and surge protectors include basic electronic components that can cause noise or other interference to the powerline adapters, but the basic two-prong adapter is just a few sicks of metal.

Also, the adapters you chose use the "AV1000" standard.  That, along with AV500 and the newer AV2 HomePlugs only use two wires for communication.  The newest HomePlug, AV2 MIMO, makes use of the grounding conductor for better reliability and faster speeds.

http://www.homeplug.org/explore-homeplug/faq-consumers/#AV2a

You should be fine.  I haven't used any of the newer Poweline/HomePlug adapters, but the older ones that I used never delivered anywhere near the speed they promised, so keep that in mind.  Maybe they are better now, but buy the books at least, your two conductor solution shouldn't be a problem.