vsivarama - I am not sure if cancer's kid is protected yet. I will leave that him/her. But as far as congressman goes - please do not feel concerned at all to show your genuine concern. Believe me, they are very courteous and genuinely will try to help you. (In 99% of the cases it is not really the congressman himself but his staff who responds and takes action on your case). These people are trained to be helpful. So do not ever worry about showing your vulnerability or genuine problem.
The only thing I would caution is - be courteous, respectful and mindful - not out of any fear - but that's what American culture is. After all this is still a favor your are going to ask the congressman's office.