Telling my daughter we are pregnant

My daughter is 4 years old and I'm 11 weeks pregnant with her sibling. I have my first Drs appt tomorrow and I plan on taking her with me. I want to give her a heads up today and tell her she will be getting a brother or sister! I just want to tell her in a special way. I have her a big sister book and a baby blanket but I want to get her something special from the baby or something.. Any ideas? How did you break the news to your children?