Need advice

Just found out on of my friend is dying, and she wants me to adopt her 3 year old autist daughter and 15 year old daughter. I can't have children of my own but love kids so much. What would you do I am having a hard time with this. I know I would love the girls with all of my heart,but at the same time I don't want to get them just because their mother dies. Please help me with this.