I believe this is very balanced. Lovingly give them the truth. Pray for them. (No theatrical shouting match with demons needed. God can expel demonic strongholds and attachments without theatrics.) Steward their heart and bring them to Christ, and He will do the work in their heart, mind, spirit ....and body if needed.To help the family work through the very REAL issues instead of condemning them as you do.
The child's same-sex preference may never go away. It's not a sin unless acted upon sexually.
They were born that way. (testosterone/estrogen imbalance) Medical assistance would help.
Sending them to "deliverance ministry" infers that the child is possessed by a demon.
That is potentially more damaging than their decision to leave the church.
Not all who lean toward same sex attraction are born that way. Very many have experienced trauma or some impactful negative event that left gaping open wounds for the enemy to take advantage of. I know, because I experienced it. Mist of y'all know my history of severe trauma (SRA/MK) that began in the womb. I experienced sexual trauma from both sexes, and was groomed to be used in that manner.
When I came to Christ at age 13, I started to let my protective walls down a tiny bit and as a result, I allowed someone I trusted to be physically close enough to hug me. Now ...prior to that, any physical closeness meant sex, violation, etc ...and so when an older woman in the church hugged me, my body responded in ways I didn't choose. Thankfully, I took it to the Lord, and He protected my heart and mind. What I was experiencing was more akin to a body memory, not a sexual attraction. (BUT, satan can and does offer lie based thinking in these types of situations and a child can believe a lie, that they are attracted to the opposite sex.)
It's good to be open to listening and ministering to any hurts, wounds, traumas that may need the Lord's healing. As well, as you mentioned, there may be hormonal imbalances that can be addressed with proper nutrition. (No child should be on synthetic hormones ...it is potentially dangerous.) Proper protein and fats will balance hormones, along with eliminating junk (processed foods, sugar, high carbs, etc).