My cousin is a historical tour guide this summer for Jamestown's 400th anniversary tours
My cousin is a historical tour guide this summer for Jamestown's 400th anniversary tours
A more concise and grammatically correct way to convey the information is to use an appositive phrase. 'My cousin, a historical tour guide, is leading tours this summer for Jamestown's 400th anniversary' clearly identifies his role and fits the sentence structure best.
cousin is a historical tour guide