hmm... it depends on when and how and where they find out
but maybe(boy) jasper after her father and a lot of fanfics have elizabeth or lizzie and ive heard katie and niva (after ziva & niomi) or maybe lacey... idk i like names staring with L
I think if Jenny ever had a son with anyone she'd call him Jasper, after her father. But for a daughter, I think she'd call it after Ziva or perhaps her own mother.
I never really thought about a boy but jasper might work or they name him after Jethro. For a girl I always thought of Kate because of Kate Todd. I also liked the name Maura just to be a little different but still very beautiful. I don't think they'll name her after ziva just because ziva is alive and it might be strange having a Siva and ziva. Maybe Gibbs would want Kelly if he didn't think of the original Kelly too much. <3