Because you are so compassionate, you would make a great advocate for children. But because you would have to come into contact with children in squalor, pain and poverty every day, I think it would take a tremendous emotional toll on you (as it would me). On the other hand, I think it would be easier for me (and maybe for you too) to deal with kids than it would to deal with animals. Seeing animals in pain would send me right over the edge into despair and grief. But with kids, maybe just because there is a much higher likelihood of being able to save them, it would be very rewarding too. Plus, with kids, they eventually become adults that are able to care for themselves, and maybe with your help, they would become advocates too.
So you have to kind of decide whether or not you could deal with all of the pain and still be able to feel like you were doing good deeds, without it killing you in the end. You would need to learn how to compartmentalize things. I could not do it.