On their birthday, cover the floor of their room with balloons while they sleep. That way they have a big surprise when they wake up.
Also on these boards
A trail of balloons leading from the bed to the birthday gift when the birthday child wakes up
Balloons are a very powerful image and can be a way of helping to create a ceremony of remembering, and a physical symbol of release. viewed as a release of the grief, a celebration of life. They can be sent with messages, notes of remembrance, poems; filled with flower or bird seeds.