Baby wish and teenagers

My partner (39) and I (37) are trying to conceive. I'm already a mom to two teenage daughters (13 and 19). They absolutely do not support our decision. The youngest is angry and refuses to talk about it, and the oldest is trying to talk us out of it in a threatening way. By threatening, I mean she doesn't want me to be stuck at home with a young child when she has kids of her own, and she says I shouldn't be allowed to see my grandchildren. She thinks we're too old and that I should be preparing for the arrival of her children instead of having my own desire for a child. I find it really hard to deal with this. Are there any other couples or families with a teenager in this or a similar situation? How do you handle it?