Personally, I agree with Adywan that, in light of the prequels, it makes more sense for Ben to want Luke to have the lightsaber. Ideally the line should be "Your father would have wanted you to have this when you were old enough," but I'm not sure that's feasible from an editing standpoint.
As for Luke and Leia discussing their mother in ROTJ, I've thought for awhile now that the continuity error Episode III introduces (i.e., that Leia remembers her mother while Luke does not, despite the fact that Luke was born first) could be remedied simply by editing Ep. III so that Leia is born first. Additionally, it may be possible to edit the scene in such a way that Padme dies before/as Luke is born, thus furthering the reason why he has no memory of his mother.
Alternatively, one could always skip Padme's death scene entirely, perhaps implying that she lived for a time with Leia on Alderaan. I'm not sure this would be possible, but it would certainly make Leia's memories more believable than suggesting she remembered her mother from her first thirty seconds of life. Perhaps Adywan could composite an image of Padme sitting with the Organas at the end of the film...