I would just grey it all down
Absolutely.
Things I did not allow and did not engage in a discussion of after the first discussion, explaining my position, answering questions, and acknowledging that my position made child/ren angry:
Binders.
Name change within the home.
Change of pronouns within the home.
Blockers/opposite sex hormones.
Discussion of surgical options. Completely off the table as a minor.
Gender clinics
What I did/do allow:
gender experiementation - wearing clothes usually associated with the other gender, make-up/no make-up, short hair/long hair - any form of gender play. Came with a huge serve of 'look at all this arty men/butch women through history who have fucked with gender while remaining grounded in the reality of their sexed bodies'
Some gender neutral language. For example, introducing dd as 'my eldest' instead of 'my daughter'. Talking about 'your sib' instead of 'your brother'. Shortening names to less feminine form (for dd). Using pet names instead of given name all the time (ds).
Privacy in therapy (with someone I felt could be trusted not to rush things).
Access to internet (maybe with a very young teen, cutting off internet would help; I judged it would make our situation worse, turn me into the 'enemy'. I know where ds is getting his info from, and I know (and have communicated) the limits to that info. I would prefer to cut him off, but made a judgement call on that. I might regret it).
~
I have had some extremely open discussions with ds about the reality of transition, including the possibility of continuing mental health issues, sterility, sexual dysfunction, ill health, a vastly reduced dating pool. He found those discussions very distressing at the time, but wanted to have them. That was a while ago.
God it's tough. Hugs to all.