I would not give up Green and a 1st next year for #11. He's a solid player, and his contract is fine -- he's expected to opt out next summer. If the added cap space would be enough to sign Melo outright, that would be a different story. But getting that space would require an additional move.
That said, I would point out that the Nuggets have a trade exception just large enough for Jeff Green, so that part of the trade is viable.