Hi I'm Finn, ftm pre-everything, and I'm currently out to my parents and my best friend

I'm visiting family in Scotland in two weeks and likely won't see them for another year so I'm planning on doing lots of coming out then.
I'll be seeing my younger cousins aged 8/11 and I'm not sure how to handle the topic with them. One also has a learning disability (I don't know exactly what) that means he doesn't cope well with change and finds it hard to get his head around some topics.
I'm also, in my opinion, cursed with a
very feminine face and figure and I currently have a longer haircut (I'm just lazy and a broke student, I'd much rather have short hair) so I'm worried that some of my family that I talk to won't take me seriously.