If children are still living at home tradition is that the child or children prepare the breakfast and serve the breakfast together with a homemade card and a flower, most likely picked in the garden.
Breakfast is served for Mum while she is still in bed.
She has probably been awake for a while listening to the sounds coming from the kitchen but will always pretend to be asleep until the breakfast is served.
The Danish bakeries are also busy making “Mors Dag” cakes so you can bring your mum a special cake on the day.