One comment stated that you should not check in any luggage
Nothing wrong with checking the luggage except you might wait a while before it gets unloaded from plane. If you think you can fit everything in your carry-on, being without shampoo, toothpaste or any other liquids then you're doing good, otherwise how you gonna bring any souvenirs from Poland if they don't fit in your carry-on? If you are flying straight from the US to Poland it would be impossible for them to lose your luggage, right? ;)