Simplify the following text for a Grade 9 native English-speaking person.
Original: Martha 's Vineyard ( adjoining the smaller Chappaquiddick Island ) is an island off the southern coast of Cape Cod , both forming a part of the Outer Lands region .
Simplified: Martha 's Vineyard ( Wampanoag : ) is an island ( including the smaller Chappaquiddick Island ) off the south of Cape Cod in New England , known for being an affluent summer colony . The islands both form a part of the Outer Lands region .