Jenna, I know what you mean about the older siblings and I'm sure they are okay with you not sending them gifts, but I bet they are thrilled that you send them cards.
I know I don't have to send E anything, but I too feel a sense of responsibility towards her. Plus I would feel wrong not acknowledging her on her birthday, etc.
S (amom) told me something once that really got me upset and I think they (aparents) are slightly bothered by it too. L, E's birthmom does not send her gifts on her birthday because as she says "she already gave her the greatest gift of all". While I agree that she did give her daughter the greatest gift of wonderful parents, that doesn't mean she shouldn't send gifts, etc. I know that birthgrandma does send gifts and I'm sure E is thrilled about that.