The Imagination Station #10 Challenge on the Hill of Fire by Marianne Hering and Nancy I. Sanders illustrated by David Hohn*

Patrick and his cousin Beth travel back to Ireland and the Druids.
They meet King Logaire and Bishop Patrick.
My second grader brought home this book from his school library and read it to himself.  He thought it was exciting and liked the part when Patrick (the cousin) was able to meet the king.