I have a bantie hen that just hatched out two chicks but isn't being the most doting mother in the world. She is with them during the day and would take your head off if you got too near, but at night she flies up to the roost and leaves them on the ground. She's only a year old herself which i guess could explain why she lacks the brains of proper parenting, or is this just what bantams do? i'm new to bantams and it also fascinates me that almost every one of my hens has gone broody, some only after their first few egg laying experiences. Are bantams natural brooders like this? or perhaps theres something in the water up here...

Put your hen and family in a floor pen at night or toward evening so she will stay with them. Some hens forget the little ones when night comes and the instinct to get up off the ground to survive takes over. If she is protected from predators in a floor pen, she should settle down with them and be satisfied. Make sure the pen is large enough to prevent predators from reaching in from the outside, and heavy enough to prevent it being turned over. You may have to weight the top of it at night. If you had put her in a pen like this as soon as she hatched her eggs, she would soon adopt it as home and take the little ones in there at night on her own.
Many bantams make very good mothers and sit often.