Welcome to Cruise Chat,
Yes, the ship should be doing something special for Easter.
If you booked in a "guarantee" than there is a good chance that you will get upgraded. It's not 100% guaranteed though. An upgrade can be simply being moved to a higher deck, or it could even be the same deck but a better location, such as midship, versus aft or forward. Sometimes it can be an outside cabin to balcony, but that isn't often.
Yes, there is a beverage package and it's $4.25 a day plus 15% gratuity. So if your cruise is seven days then 7 X $4.25. You receive a mug with the package but you don't have to carry the mug around with you. They put a sticker on your cruise card. 15% gratuity is added to any beverage/alcohol drink regardless if it's a package or individual drink. People that drink a lot of soda, (at least three a day) benefit from the package. The package is per person and not shared.
I've never used the laundry so I can't answer that question.
I was just at the Sheraton Ft Lauderdale for a conference in November. It is a wonderful hotel.