Jan, Thank you, that is a great idea to celebrate Valentine's Day!
Papa, you are welcome for the reply. Janfred's suggestion of a specialty restaurant for dinner is spot on for Valentine's Day as an option. The Freedom has the Sun King (reservations-recommended) Steakhouse. The charge is $30 per person and well worth it, especially for a special occasion. The Steakhouses don't always get booked to capacity for the dining times. However, it could with it being Valentine's Day.
So, if you decide on doing this, here is what I recommend;
Go on the Carnival site, then My Cruise - My Reservation. There should be a place to request a reservation at the Steakhouse for that date. They no longer confirm the online requests by email. If you have a Travel Agent they can take care of this for you. Now, when you first get on the ship check to make sure you are on the reservation list.