They see something in you that comforts them, and they trust you. Follow your heart, and don't be afraid to cry in front of your friends. Tears are cathartic and sometimes are the only way to get through difficult situations. This is a difficult situation for you, but you have the oportunity to soften the blow for these kids just by "being there". That's huge praise, my friend. The trust of a child is a blessing that's immeasurable....cherish it. You have a chance here to shape their lives. Just be there with them. Cry with them ..... talk with them...listen to them. Just remember to look past the physical ailments and look into their eyes. Your friend is still there, inside all the changes you may see on the outside.
God bless you ....... I know you're struggling, but you'll get through this. Lean on each other. You might be surprised at how strong and wise kids can be sometimes.