Also, if it wasn't for Obi Wan describing Luke's father as "the best star pilot in the galaxy, a cunning warrior, a good friend" in A New Hope, I'd go so far as to say that all that would need doing to preserve the impact in ESB would be to remove all reference to the name Skywalker in the PT as well as the twins being born/rehomed as this would remove any connection between Anakin and Luke.

As it stands, it's obvious who Obi Wan is talking about, even though he was anything but "a good friend".