Hey, I get it. Coming out isn't easy. I'm trans (nonbinary) and aromantic, and coming out to my family has been hard, but with enough explanation and confidence its been so much better. For you, I only have one main thing to say, and it's something that I've had to learn: Don't rush yourself. Don't force yourself to come out to people if you aren't ready.
As WN said, if you believe that coming out to certain family members will put you in potentially abusive or toxic environments, then don't. No matter how exciting and important coming out is, getting stuck in those environments is very unhealthy and can really diminish your self-esteem and confidence.
Also, your mum and siblings sound like really great people. I'm glad you have them in your life. They sound like they just need a bit of explaining. Maybe you could sit them down (family meeting, perhaps?), crack a few jokes, maybe gay/queer jokes, and then get to the point. All they need is some explaining and im sure its going to be okay.
Or you could do your idea, which is also very cool. I love LGBTQ+ jokes :)
I wish you the best with coming out, my friend. Im sure it will be alright. Just know that even if some of them don't accept you, all of us on KT will. We all have to/have had to go through the same things you are, so we understand 100%. Its all part of the journey.
- Dino (he/they/xe)