agree with darth bizarro
not a parent, but i think just pop in star wars and watch it on your own...if they get curious, they'll sit down and watch it with you. Friend of mine says she did that with her kids. Didn't force PT or OT. Last i heard, PT is at a disadvantage cuz there is no Chewie :)
Its also interesting to note that many parents of young kids find the Episode III scene with anakin ready to kill the younglings a huge turn-off and won't let them watch it becuase of that!
anway, kids today watching OT would be like me when i first saw the Wizard of Oz 30 years ago. it didn't matter to me that the film was made in 1939 and I was watching it for the first time in 1981. It still worked.
Now visual effects have increased exponentially from 1977-2011 compared to 1939 to 1981, and there are much more fantasy films and video games nowadays (my dad once said that when Star Wars came out the only movie that could compare was in fact The Wizard of Oz) so it may not be the best analogy.
but i would never sell the OT short. and if they still genuinely like the PT, que sera sera.
But they have to honestly like it better - not because they went on TFN and read that "lucas is a genius for making the TPM space battle suck ass otherwise it would overshadow the OT space battles which occur much later when you watch the films in numerical order!" or "it totally makes sense that anakin and padme have no chemistry cuz its supposed to be a failed romance, lucas is a genius!!"