Did you also capture Evil Rosa, and get a Chocolate Bunny for a reward? If you did and have the Bunny, it'll show it in your Inventory.
That's the only reason that I can think of for the ? still being there.
The 250 Easter Eggs get returned to the Easter Bunny to get your Easter Ribbon and Easter Bunny Pet.

If you didn't capture Evil Rosa yet, Inspector Kaine should give you a Quest to find her after you finish the Treasure Maps, and find all of the clues for him. If you've done that, there should be a gate on the right side of The Easter Meadow leading to The East-er Meadow. That's where Evil Rosa is, and you just go take her down. She's got all of the eggs. :)