Or that could be Phetus. My son, and later my nephew, were dubbed the Kid. I even had a psychedelic poster of a little kid in a beret with a slingshot in his pocket with a caption which said "The Kid" which we got after Colin was born. I never knew the gender ahead of time and I am glad that we didn't have that option.

You could always go with the s/he, pronounced Sheehee, but I 'spose someone might think you were giving it a family surname of Sheehey.

Little Critter? Tiny Tot? Lil' Sprout? Pronouns are tough for non-gender, but they always sound better in another language: German it is "das" (daws).

Congratulations! Anudder Little Mudder! Yippee!