This is a great request and there are many ways in which you can go. In light of this, let me give you a few suggestions on power and leadership.
First, you might want to talk about the importance of service. You can say something that touches upon the idea that what makes a great leader is the idea of a servant leader. We see this to a certain degree in Ralph, as he seeks to help people. However, when it comes to Ralph, there is very little notion of being a servant leader. He wants power for the sake of power. If you recall, he was very angry not being elected leader in the beginning of the book.
Second, if you want to use the idea of power, then you can talk about what power should be used for. Power should be used to help the group, rather than used for personal gain. Ralph seeks to use his elected role to figure out a rescue plan and help the boys until that time. Jack wants to use his power to get his own way, particularly in the hunt.
Thid, there is a famous quote: "Absolute power corrupts absolutely." You might want to work this in, as Ralph shares his power. Jack take power and rarely shares it.