Ugh they express this blatant propaganda in a cartoon..?! Because the issues involving children are just so simple, of course a cartoon is appropriate 
I don’t think it’s ethical for broadcasters, newspapers etc to refer to ‘trans children’ at all. They wouldn’t refer to ‘Labour children’ or ‘Conservative children’ or ‘Communist children’ or ‘Fascist children’ would they?
(and IMHO they shouldn’t actually refer to ‘religious’ children either. )
These are all adult concepts, beliefs and labels that kids are going along with.
The kids may well passionately believe in these things very strongly but they are kids - by definition they are without the life experience, judgement or maturity to really understand or possess the freedom to think what they think for themselves, as distinct to what the adults around them think. They are by definition impressionable, highly sensitive to and easily influenced by the views around them. As all humans are but children particularly so.
So instead of saying ‘trans child’ which is a political concept, newspaper should go no further than to say ‘child from a family and/or social environment that believes in genderism’.
Just like they would say ‘child from a Christian family’ or ‘child from a family of long-standing Liberal Democrats’ or whatever.
These are all adult views and beliefs, which the children that the Guardian would irresponsibly call ‘trans children’ are brought up into, and/or exposed to via social media or school.
It should be against editorial guidelines to ascribe political views to any child under 18.
The social environment thing is so insidious. It’s totally the elephant in the room yet we know that (mostly female) kids are being rushed through a system to drug, permanently alter and potentially mutilate their normal natural bodies as a result. Where is the proper psychological support for them? Why is the Guardian not acting more responsibly about this? Do they not know that there is a national scandal brewing and the Times has been exposing via professionals’ whistleblowing, the very very worrying reality for these kids once they are given this label?!