Step Parent Mommas?

Ivy
I step parent a 10 year-old girl and a 7 year old boy. This is my first baby (and likely my last, I'm 35).  All of us get along pretty fantastically most of the time but I'm a little curious (and freaked out, admittedly) about how a baby in the mix is going to change things. Anybody in the same boat or with any personal experience with this?
I'm usually pretty shy so stepping out of my comfort zone...! :)