We celebrated our parents 50th last April with a family cruise. My sister sent a form letter out to all their friends 6 months prior to the cruise requesting that they write down a funny story or memory of my parents. We provided them with one page and a stamped return envelope with a deadline to return by. Everyone in the family also wrote a page. Then my sister took all the letters and bound them into a book. My parents loved it.
We also got an edible picture made of their wedding picture and their 50th anniversary picture and gave it to the maitre'd and they made a cake out of it (no charge).
I am a quilter so I made them a picture quilt with over 200 pictures from the last 50 years. It was alot of work but worth it when I saw the expressions on their faces.
You can reserve a room on the ship for special events and could order up an afternoon tea(check with your travel agent or the cruiseline directly). We just went to one of the bars that didn't open until later and opened the gifts there.
I also contacted our Prime Minister(I live in Canada), Governor General, and various other local politicians and they all sent letters of congrats. We also contacted so of their favorite actors and actresses but only one replied. In all fairness though a few were not in good health.
We also had a family portrait taken onboard.
I took 5oth Anniversary balloons and decorations on board and decorated their room and the room steward made swans with a heart in the middle out of towels.
We also ordered them a tropical flower arrangement that was in their room when they arrived onboard.
We had a great time together and family members still talk about it.