Hi, Susan! I checked with my own Tween with regard to the Pirate Adventure, and was told that it's kind of a cool thing, but it's really for "little kids". I will say that I've taken my nephews and my daughters at various times, and the age range seems to be the nine and under crowd for the most part, so your nine year old may not feel too old. The 11 year old may feel more comfortable being on the upper limit of the age group because he is with his brother. It really is a fun adventure, though, so I'd probably describe it to the boys and see how they felt. Every kid is different!
If they are really into pirates, you may want to do a Pirates and Pals fireworks voyage with them. This is more about snacks and an awesome show than about fantasy and imagination, and that seems to work better for some Tweens. The cruise leaves from the Contemporary hotel, after a snack buffet at the hotel. The cruise takes you out to see the Electric Water Pageant, followed by a stop at the perfect spot for fireworks from the Magic Kingdom. It's great fun, within singing and joke telling, and I think kids of any age might enjoy this.
Another thing you could do with the boys is the Wild Africa Trek. This is sort of like a backstage tour through the Harambe Wildlife Reserve at Disney's Animal Kingdom. You'll navigate a rope bridge, check out the animals from a private safari camp, and navigate the reserve on a bushwalk. This is another fun for everyone type of event, and great for kids this age!
Another suggestion - let the kids browse the
WALT DISNEY WORLD website. That might give them some more ideas!