Fedex might be more reliable than the post office. But to be on the safe side ask the people you want to deal with about regaining citizenship if they would accept notarized duplicates. This way, you still have the originals in your possession in case the duplicates get lost or destroyed enroute.
I knew of someone that did a family tree for someone who had sent originals by mail and the originals got destroyed by accident. Any information contained in the originals got lost because of that. When you look at the originals ask yourself how easy would it be to replace them for one reason or another such as being destroyed by fire or stolen. Good luck.

 

It was probably me. This way, if something happens to the duplicates then you can get more copies done. But if something happens to the originals and if you can't get replacements for them then you are out of luck. Chances are that Lukasz can print out the scans and notarize them, but it would be nice to locate someone near you that can make copies and notarize them if it is needed. That way, if the system in Poland will not accept the notarized scanned documents, then you are still covered because you started the process already and not losing time. Also, on a side note, by having the originals scanned/copied, then you can put the originals put away into a safety deposit box for safe keeping against fire, theft or other unforeseen problems. I am not trying to be a pessimist, but why take chances with originals.