Again, these are the impressions left by a couple of the books and it all depends on if you give the novels much if any canonical weight in your view of the Star Wars universe. I pick and choose myself but Palpatine knowing the truth but deliberately lying to Vader in order to crush his heart and spirit seems like something the Emperor would do....and gladly.
That's all well and good, but do the books explain why this super-smart Emperor guy decided to let Luke and Leia live? If he knows Padme wasn't dead, then surely he could use the same superpowers to figure out the two kids are alive. Doesn't make sense that he'd let them grow up unsupervised.
Also, he seems genuinely unaware that Luke was alive in Empire Strikes Back. But he does make the prudent decision to decide to supplant Vader with his son. The Emperor never seems to know that Leia is also Vader's child, either.