Hi Jonina!
First, major congrats to your first Disney vacation! You are going to bring so many memories back home you won't be able to keep count! :-) Make sure you keep those cameras loaded and clicking away...
By day pass, if you're referring to Theme Park admission, then yes, any Tour or Special Experience is going to cost you extra.
At this writing, the Pirates League will run you $29.95 per person. It is, however, a cool experience. And although both boys and girls can enjoy this experience, I've always looked at the Pirates League as a great alternative for boys compared to, say, Bibbidi Bobbidi Boutique.
If you click here this will give you a run down of Tours and Special Experiences at the Magic Kingdom, including cost.
Hope you and your family have a magical time!