What are some good songs for a departing senior to her family?

When school comes along, I'll be a senior, and I want to sing something to my family for one of our choir performances. Something to show how much they mean to me, or that I'll never forget what they have done for me, or something else along those lines. I'm a soprano and can't go very low at all, but I'm open to all ideas. The song can be any style, I just want it to really mean something special.