There are two big questions here, and both of them are reflections—that is, they're asking for your own thoughts and feelings about the material. That makes it quite difficult for others to guide you explicitly—you need to give your own responses here. eNotes policy also prevents educators from answering more than one question in one post. So, I'll go through the poem first, suggesting how you might respond to it, and then give some suggestions as to how to tackle the second part of the assignment.
The poem is written from the perspective of a girl named Wendy, who has found herself drawn to help "lost boys," as Wendy did. Having seen the example of the little "hausfrau" Wendy in Barrie's book—able to connect body to soul in her lost boys, stitching shadows to her heels—she feels sure ("I knew") she could do the same.
In reality, however, things aren't this simple. I feel that the poem implies the "boys" are not children, but young men the narrator has partnered with as a young girl. The poem seems to be describing the drive in some women toward helping or "fixing" broken men, being sure that they will be the one to heal them. This narrator finds she isn't able to do this—it isn't as easy as Wendy made it look. Eventually, she "grew and flew away," and the lost boys didn't grow up, but died instead. Now, the narrator is old enough to realize it was not her fault—this is how things normally happen.
The final stanza of the poem, however, suggests that the narrator now approaches lost boys differently. Rather than stitching their own shadows to them, she now attaches her own shadow, "my shadow," to keep them safe. It is, perhaps, still possible to save these people. The last line alludes to the Barrie quotation "Clap your hands if you believe in fairies." The narrator, she says, does.
So, how to respond to this poem? Do you relate to the narrator's plight? Do you think she's right? Do you sympathize with her? Do you feel it's sexist, for example, that there's an expectation that women should look after men in this way?
The second part of your assignment asks you to write a response to Peter Pan, and it's very open-ended. This is good—it lets you be creative. You could write your own poem from the perspective of one of the characters, perhaps in the style of Froud's. Or, is there a character you wanted to know more about? Maybe one of the lost boys and what happened to him? Or Captain Hook—who was he before he met Peter and the boys? A really great way to respond to a text is to think about it from a different point of view—tell a story that isn't explicated in the text itself.
I hope this helps!