Thank you so much for your email. From what I read, I am deeply touched by your closeness to your parents and commend you for your desire to give away to a Polish museum. Your desire to give is more than half the journey to simplify.
I normally follow a 3-S rule when it comes to clutter in general. I ask myself if I :
1) will use the item in Six months to one year
2) have Storage space to keep the item
3) have System of retrieval when I need the item right away.
If I say yes to all three, I normally keep the item.
When it comes to keeping things with sentimental value, I normally follow a 3-H rule. I normally keep items anything that reflect:
1) History - family photographs, heirlooms, journals, etc.
2) Heritage - like art or memorabilia that reflect your family's ethnic background
3) Holiness - books and sacred images
I do however, give myself a limit as far as storage units for all my 3-H items. For example, I give myself a small curio for items that reflect my heritage. I also keep a certain number of religious images per room and a curio drawer to keep books for spiritual reading. Anything above and beyond that I try to give away to family members or very close friends.
Thank you again for your email and I hope this helps! May God bless you in your journey to simplify!