If, for whatever reason, you want to make coming-out in person work, you could consider inviting them for dinner or to a café to not have "too many people around". Or come out to your siblings first, possibly ensuring you their support when coming out to your parents. In any case, I have noticed that it helps to have supportive people around, so maybe bring a friend or some. If those you come out to are overwhelmed and don't know how to react, seeing how your supportive friends behave towards you gives them guidance.
I can't speak about coming out to family via text, but if it helps, here's my coming out email at work:
subject: It's a girl! (Spoiler, click to expand)
dear colleagues,
I'd like to inform you that I got a new name that suits me better. My name is . Please call me accordingly, I'm looking forward to it!
sincerely,
Nobody explicitly commented on it, but the subject gave me a smile for quite some days. Especially as it's sets up a wrong expectation about what the email entails and as the message body itself doesn't even mention gender or pronouns.
However, I can imagine that parents might be less nonchalant about implying you're becoming a parent, when you're not. So maybe choose not to do that.