I've incubated Serama eggs under a standard broody and they did fine. The broody is usually careful not to step on her eggs.
Here's a picture of my Welsummer hen with her chicks - they all hatched within 24 hours of each other and are about 3 weeks old now - the black ones are pure Serama, the colorful ones are Serama/OEGB mix and there's some mix-bred standard sized chicks in there, too.