Cruise Wedding

My fiancé and I recently decided to change our plans from a traditional wedding to a cruise wedding, The big motivator for us was to save money. The second being to help relieve stress from the planning process. We live near Baltimore, and would like to choose that as our embarking port. Therefore, we are between Carnival Cruises and Royal Caribbean. We have not yet engaged in conversation with either, but based on the brochures, they seem to be roughly about the same price for the wedding packages. Carnival is more up front with the time limitations. We plan on getting married on embarkment day, so some of the guests can choose to sail or not sail with us. Does anyone know what the average reception time is for Royal Caribbean? Carnival clearly limits the time to about 15-20 minutes for the ceremony and 1.5 hrs for the reception. Wondering if it is basically the same for Royal Caribbean. Also, if someone has used Royal Caribbean which was the ideal photography package because they base their process on time (2-5 hours of photography). Finally, does anyone have any do's and don'ts overall for having a cruise wedding on either ship line?