As always, you get what you pay for. A newer ship with more room, more amenities, etc. is going to cost more. The rates are generally based on double occupancy, per person, but be sure to ask if the room is actually a double room or if it is designed to accommodate 3 - 4 passengers. Some passengers who thought they had a great price on their cabin got on-board to find that they had strangers for roomates, who also were as unpleasantly surprised, to discover the cruise line put them together unexpectedly. Specific senior's rates are generally not the norm, but there are designated senior cruises.
Entertainment is great on cruise ships.
Many ships have a wide variety of entertainment options, such as video arcades, piano and dance bars, special dinners and theme parties, and all have some form of acivities director and information desk to help you make the most of your journey. And today, most cruise lines offer Las Vegas or Monte Carlo style casino's on-board. All kinds of duty free merchandise can be purchased. Everything from hand-made crafts and jewellry, to clothing and souveniers are available. The list is endless, and the choices can be both numerous and unique.