Sending a gift with card is the perfect thing to do! You must treat the baby's birth just as you would any other. Every baby is a miracle and a time to celebrate.
I have an 8 1/2 month old baby girl that was born with Trisomy 21 (Down Syndrome). She is such a beautiful baby girl. We were blessed that she doesn't have any health problems whatsoever and continues to do very well. We could not love her anymore than we do.
We didn't know prior to her birth that she had this. There were markers, but, I did not undergoe a amnio to see for sure. I had the quad screen and a ton of Level 2 ultrasounds. We were given a 20% chance of her having DS.
In any case, your friend will be in shock initially, as were we, and that may move over to denial (until the genetic test comes back positive), and then she'll go through all the grieving signs that one goes through when they experience a death in the family. What happens is, when one gives birth to a baby with DS, they grieve for what they dreamed of having; a baby with no genetic condition; a healthy baby.
With the support of you and her family and friends, she will get though this, and, will come to realize that raising a baby with Down Syndrome is truely a gift.
As for doing something for her parents, there really isn't a need. And you are right, no one who has a family member with DS wants pity.
Our baby may have down syndrome, and it will always play a little part of who she is, but, it is not a horrible thing. She will do just fine because she has a family who loves her, and has all the early childhood intervention she can get. We have her in a gymnastics class, swimming class and music class, all for "avereage" kids. Sure, she does play with some children with DS, but, we make sure she interacts with all children.
Make sure your friend gets involved in a DS group. Her doctors should recommend it.