Tony Bradman 
Attack of the Vikings 

Finn wants to be a Viking warrior, and seek adventure and glory in far-off lands, not become chieftan of a farming village like his father. But then, when his father has been summoned away to another island, Finn is left in charge, and danger strikes. With the village under siege and only Finn and his friends to protect it, can he save the day and learn what it really means to have the blood of a Viking?