I attended a baby shower in November and wanted to do a big brother/little sister shirt set because I've been dying to use these Fabric Finders tri-checks. The only problem was that the mommy kept the baby girl's name a secret until after she was born. I did the exact same thing when expecting my two kids, so I had no beef with her! :)
My solution -- make the big brother shirt to be unwrapped at the shower, and include a blank onesie with design image and applique fabrics for baby sister. So first I made Maddox's shirt, and he was able to wear it to the hospital when visiting his new sister:
Big Brother Design is from Applique Momma. I added his name with Embird Alphabet #8.
Little Sister Design is from AM, too.