aw :( the best thing you can do in your notes is to express to them it's not at all their fault; you were suffering inside and didn't want to trouble them any longer. make it clear you love them a lot. I understand as when I made my ctb plan last wednesday, I felt awful thinking about my family's reaction after.
I tried to make myself feel better by realizing that ...
1) if not now, eventually I'll die. we all will die someday.
2) all families experience grieve and loss of loved ones. that's life. this made me feel a bit better.
3) even if I do stay alive to keep them happy, I'll never progress in life because I'm only living for them, not myself.
4) reconsider suicide. plan out your life if you stayed alive, see how you like it. I tried doing this only to come to the conclusion that I'd get nowhere and accomplish nothing. this might be different for you, but if you find yourself feeling like they aren't enough motivation to keep yourself going, then it's hard to validate staying alive solely for them.
5) getting all the pain and tears out asap. at first, I kept bawling my eyes out when I thought about them getting the news, but over the course of a few days after finalizing my ctb, I was able to let the grieve go some and stop caring so much about how they felt.
I hope this helps you to feel a bit better. I feel like too many on this site will tell you don't feel bad or feel guilty, but many here also don't really have caring families so it's easy for them to say. it'd be nice if your family's love was enough to keep going but living for others when all you want to do is die is so miserable. best of luck to you :)