I don't know how old these kids are but I have two great songs for you. One is called the Raven Banner: Sigurd the Jarl of the Orkney Isles, Has called to his Banner a Viking band; And sailed to Dublin to make himself King of the Irish lands....
Another is a Saxon song, Song of the Shield Wall: Hasten, O sea-stead, over the swan road. Foamy-necked ship o'er the froth of the sea! Hengest, has called us from Gotland and Frisia To Vortigern's country, his army to be.......
Lots of fun to sing too. Try http://www.hom.net/~brand/songs.html for full lyrics and tune samples