You get to decide how you come out, that's up to you. If safety or privacy or feelings are a concern, then it's totally valid to put some distance between you.
As a parent, I'd probably rather a paper letter than email. An email feels kind of impersonal. Also if they're like my parents, they rarely check their inbox. Not knowing if they've read it and chose not to acknowledge it versus just not having seen it - that's a recipe for anxiety, personally