I have never sailed with Virgin but have done Princess/Carnival/RCL/NCL and all of them offered events for singles meet and greets. There is a daily schedule online that will tell you what and when they are. Try googling your ship and there are website that post old daily schedules for cruises. It might not be identical but it will give you an idea of what a day will look like. Just don't wear anything with a pineapple or flamingo on the cruise unless you are looking to swing

As for the drink package, I think you need to look at it as a math equation. For example, say you would drink 6 drinks per day on sea days, and 3 on port days. Multiply them by the drink prices (try googling to see if you can find), and see what your total comes out to. Then compare it to the price of the drink package and see what it is worth. Its really that simple (although a complex equation since not every drink is the same price)