I'm coming out to my parents via letter in a couple weeks.

I am 21 and have known since I was 13. My parents are both very religious and have bashed the gay community my entire life growing up. I have no doubt they will continue to love me and support me after having sometime to process. However, I am very fearful they would say something if I came out to them in person which would stick with me for the rest of my life and they would regret for the rest of theirs. I look at the letter as an opportunity for them to avoid that after taking a few hours to process it. I thought about sending a LGBT+ book for parents with it. Does anyone have a suggestion?