I agree, full transit is the way to go as everyone suggests.
With your anniversary in February, that time of year may not be an option. You have to remember most of these cruises are repositions from Alaska to the Caribbean or vise versa. Therefore you will have to go in late winter/spring or late summer/fall. Other times are pretty rare and not done routinely, since it cost the ships plenty for traversing the canal.
O F C'er