Only one "to" in needed.
To whom will the package be delivered?
Adding another "to" at the end is grammatically incorrect. Also, sentences should generally not end in a preposition, though a native speaker is likely to say:
Who will the package be delivered to?
In an informal setting, the second sentence is preferable if spoken; the first might make you sound pretentious, at least in America. Some teach that ending a sentence with a preposition is always grammatically incorrect, which is a vestige of Latin influence and is debatable.