Help getting from Hotel Santa Croce Boutique in Venice to the Marittima Cruise Ship Port

Yeah, you should tell the location exactly. So that someone might be able to help you. All the best!

I guess Venice

Ask the hotel staff? You cannot possibly be the first guest that had the cruise port as a destination

Here is the "How to reach us" from Santa Croce Boutique web page:

https://www.santacroceboutiquehotel.com/en/how-to-reach-us/

From the Cruise ship terminal, you would take the People Mover to Piazzle de Roma
then take the Vaporetto Line #1 to the Riva de Biasio stop and then follow the hotel's directions down side walkways to the hotel. Google says it's 6 minute walk

EDIT: whoops, I just read you want to go the other way from the hotel to cruise terminal. So just reverse it. Walk to the Riva de Biaso vaporetto stop, take a vaporetto to Piazzle de Roma, walk across the parking lot to the People Mover.

...and will I have difficulty pulling the luggage...

I would not want to walk all the way from the hotel with luggage. The easiest way is to take the vaporetto to Piazzale Roma. On the far side of the big open space is a white building that houses the people mover. Take it to the first stop and then walk from there. If you have luggage that the cruise line is going to load and send to your cabin, look really well for the drop off point. Last time we cruised from there it was hard to spot. Things might have changed however. Google maps has street views of the area so you can check it our and orient yourself beforehand.