Seems like a lot to give up. I mean, I know, bird in the hand, and all, and I'm glad you kept Grubauer, Bowey, and Djoos, from that perspective.
But this is two firsts, a second, a third, and three solid AHL prospects who will each play some games with the Capitals next year, plus the team's toughest defenseman for a less tough defenseman that scores less, a guy they drafted fifteen years ago who mostly scores on the power play but won't play on the power play, and a winger who scores at a slightly slower pace than Connolly or Burakovsky, and has one less goal than Connolly. Green at even strength scores slower than Bowey. There's something to be said for adding two more guys with experience, for the playoffs, but giving up two first round picks, a second pick, and three solid prospects to do it? Nah.
Check out the "Production" stat here, where they divid points by total minutes played:
http://www.espn.com/nhl/player/_/id/5479/brett-connolly
http://www.espn.com/nhl/player/_/id/3042044/andre-burakovsky
http://www.espn.com/nhl/player/_/id/5479/brett-connolly
I think the Caps could look at giving up Siegentaler and a 2nd for Athanasiou as a huge improvement. Hjalmarsson is worse at regaining possession than Orpik by over a hundred hits, so far this year, and the remaining difference in their contracts doesn't make up for it.
Green plays a lot of minutes, and has three points in his last five games, so I wouldn't say no to adding him for free, but I wouldn't give more than about a 3rd pick if Detroit isn't just interested in dumping salary.
Check out his playoff boxcars. In the 'aughts he was almost a point a game player in the playoffs. Since the Spring of 2012, he has 12 points in 14 playoff games. In the Spring of 2016 with Detroit, he played 16 minutes a night, for five games, and posted 1G, 1A, -1, 10PIM.
https://www.hockey-reference.com/players/g/greenmi03.html
I think Bowey might do better this year than Green, which is okay, because Kempny might take Bowey's place.