There are a number of 'side-by-side' translations available. Barron's has a series of them, I know, and "No Fear Shakespeare" is another brand-name of a series like this.
They are arranged so as to have the original (well, mostly First Folio, anyway) text on the right hand page, and on the left, or facing, page, is a modern language translation, often with notes that explain some of the idiomatic expressions and such.
Do be aware that ALL of Shakespeare's canon contains themes, language, and content which is both bawdy and very adult in nature.
DD began reading R+J and Othello this way when she was about 6-8yo, I know. Dream, we kind of insisted on the original, since the language in that one is SO special.
