Hi Virginia,
Welcome back to the Moms Panel! We're glad you're hEAR!
You're asking about two of my all-time favorite experiences at the Magic Kingdom! You are going to LOVE Mickey's Not-So-Scary Halloween Party (MNSSHP). Since you have an extra regular admission ticket that you can use on the same day that that you're attending MNSSHP I think it is an excellent idea to sign your kids up for
The Pirates League. In fact, if you're all going to be pirates, then you should sign up too.
The Pirates League is a very popular experience and with good reason - it is awesome! If you want to do this on the same day that you are attending MNSSHP, I'd recommend that you make your reservations now by calling 407-WDW-CREW.
If you don't plan to leave the Magic Kingdom in between your pirate makeovers and the time MNSSHP begins, make sure you bring your MNSSHP event tickets with you. Also if you plan to stay in the park all day and into the evening and don't want to wear your pirate skivvies all day, you could rent a locker to store them until you're ready to make your pirate transformation and take over the Magic Kingdom. One more tip in case you plan to visit all day and into the evening, I'd get as many attractions accomplished during the day so that you can focus on the special events available only during MNSSHP.
Wishing you many spooktacular, piratical memories :-) Allison