Well, my folks are both from Poland, so I could hopefully tell you what’s traditional at least from their part of Poland (the south). Horseradish, sausages, hard-boiled eggs, salt, and butter (all of which are blessed before the meal, usually during the Holy Saturday blessing of the eggs) occupy a prominent place at the table. The sausages we usually get blessed are long, skinny dried ones called kabanos. Also, there’s usually a spread of sliced Polish ham and Polish rye bread to go along with the rest of those items.
A soup course of white borsch/zurek is usual. Zurek is a mildly sour soup that’s made by fermenting some rye flour and water (kind of a pickle lactic-acid fermentation) for several days, adding garlic, spices, and stock to complete the base, and then you cook it with potatoes, sausage (either white or smoked Polish sausage), and hard boiled eggs. If you live near a Polish grocery/deli, you may be able to find a jar of the fermented zakwas to start your soup, or the powdered version of the soup are often pretty good, as well, although I usually add some vinegar to bring the tartness up a bit.
For the main course, we do a roast of some sort. I believe the traditional meats are pork and veal, although for the last few years we’ve done lamb. Actually, here’s a pretty decent Easter menu I found. I’m not sure about the asparagus in tomato and yogurt, but the rest is pretty commonly found at the Easter table. The Easter Soup recipe on that page is an approximation of zurek and a pretty poor one at that, from what I can see. This would be a more authentic recipe, although the Polish Easter version will also contain horseradish and the blessed, hardboiled eggs in its ingredients.
What else? I don’t ever recall having pierogi at a typical Easter Sunday meal, but I don’t see why you couldn’t do it. Scanning the web indicates that some people do it pierogi on Easter Sunday, so it may just be a thing my family doesn’t do.
And for the correct Polish spellings of various dishes in this thread (obviously, there are accepted American spellings of these dishes as well), with accents, should anyone need to google them:
Czernina/czarnina - Polish duck blood soup
Gałąbki - “little pigeons”, stuffed cabbages
Kolaczki - little Polish cookies/pastries
żurek/barszcz biały - Polish sour soup
Chruściki - Polish bow-tie cookies (“kruschiki”)
And chrzan (“horseradish”) is better rendered as “KSHAHN” in English, although the initial consonant is a guttural “h,” kind of like in “loch”.