Some cruise lines are against this, but many will accommodate. All you have to do is ask the Wedding Dept! Today I went with a bride on board Carnival Spirit. We arrived at noon to board the ship. It was a bit difficult to find someone who knew we were guests. So please be patient it can be difficult getting to the right person. Once onboard we were on our own. I found out later the group coordinator missed us getting on board so poor thing was looking for us. She finally did catch up to us 30 minutes before we had to leave.
I would highly suggest bringing your Travel Agent with you. I was able to show them the cabins prior to guests going to the rooms. Since I have done many ship tours I know how this can be done. I also brought a deck plan with me. This is your bible while on a tour. I used it many times to get around the ship and find some of the suites. One way to make the most of your time. We had time to see the cabins, ship, and even have lunch at the buffet.
One of the highlights was the spa. When your getting married on a ship you don’t have time to do the normal spa tour. My bride was able to have the tour now and not miss out.
It was a great day and well worth the time for the bride. So just ask!