I am assuming you want an honest answer, not one to make you feel good. My honest answer is I think your question is irrelevant. The relevant question is do you take yourself seriously when you say you are trans? In my 70 years on this planet, two very important things I’ve learned is (1) Never let anyone else’s opinion of you become your reality. Your reality is you believing in yourself and (2) Blood doesn’t make you family, blood just makes you related. Family is that group of people that believe in you, support your decisions and assist you in obtaining your goals.
I suspect you already know the answer to your question. Are your parents the type of people that will support you in any decision you make, even if they’re uncomfortable with it or don’t think it’s a good idea or are they the type of people who will judge and question everything you say? If they’re part of the first group, there shouldn’t be any issues at all. If they’re part of the 2nd group, I would suggest re-reading what DeeAnn wrote above because there is a lot of good information there. Do you have friend that you are out to? Ask them to help you role play and take the devil’s advocate side. Try to think of every possible negative comment that might be said and figure out how you will respond to it. Like DeeAnn said, you don’t want to write an essay. You probably do want to have some note cards with bullet points on them to help you remember things you want to bring up or potential answers to negative comments and questions.
Also I would suggest thinking a lot about when you first started feeling something wasn’t quite right. How old were you and what was it that make you think you might be somehow different? I knew by the time I was 6 that I wasn’t like all the other male children that were my peers. I didn’t know what the difference was, I just knew I wasn’t interested in the boy things and I was interested in the girl things, which wasn’t going to happen back then. This was in 1959 and back then most of the world had never heard of the idea of multiple types of gender identities and they only recognized two different types of sexual attraction, hetero and homo, and if you declared yourself homo you’d end up in a very unpleasant locked psychiatric facility and pumped so full of drugs you couldn’t remember your name. It took me almost 40 years, including 3 working with some very good psychiatrists, a couple more as co-facilitator for 2 different self help groups, and several more years of auditing psyche classes before I had a true understanding of who and what I was. So if you expect any questions or denials, make a list of every time you thought something was wrong and why, and this might be one of those places where you want to have as many events and details as possible.
Above all else, believe in yourself and control the conversation. You will have much better luck convincing doubters if you don’t show any cracks in your own belief.
Good luck. I hope all your fears turn out to be unreal fantasy.