"In Wales on March 1st most schools hold an eistedfodd where the cultural arts are celebrated with singing (solo and group), music, poetry and dance. Women especially young girls dress up in a welsh national costume. These vary but consists of a black tall hat, skirt (often red), white blouse, a long waistcoat, apron and shawl. A daffodil or leek ( Welsh national emblem) is worn by most Welsh people on St David's Day." from dltk-kids.com.
The Story of Saint David, printable for children.
Learn more about Wales and St. David's Day
Nice link with cute crafts. Here are a few:
Welsh recipes, Yorkshire Pudding is among them.
Daffodil(AKA: Lent Lily) Stories, Poems and Activities by Grade, Some Lesson Plans