Or talk to the Cruise Director and see if there's someway they can work the proposal into one of their shows. Maybe even during the ice show or in the main show lounge. They'll even schedule the photographer to be there to record the event. They love doing stuff like this as it involves the passengers and makes their cruise more memorable - not to mention it'll be something neither of you will ever forget.
Your agent can get in touch with the people on the ship so you can begin the planning ahead of time.
Sounds very exciting and romantic!
47 Cruises & Counting! Favorites: Paul Gauguin to Tahiti: Uniworld River Cruises in Europe; any of the Celebrity Solstice-class ships; Holland America for 12-nights in the Baltics & Russia; RCCL for 14-night Greek Isles, Turkey, & Croatia; Holland America for 14-day Alaska cruisetour; 10-night Canada/New England cruise; 21 days in Hawaii including a 7-night NCL cruise; Oceania for 25 days in Asia; & 3 months touring Europe by train. And many days spent in all-inclusive resorts!