I don't see why the Wild go for Krejci. It's unneeded. They already have a borderline top line center in Koivu. Plus Seidenberg is a pretty liked piece in Boston. PMB and Krejci are both injury prone so I say keep the devil you know.
The last trade is just bad for Washington. Carlson is viewed as a top 4 dman with top PP ability. I can't see them trading him. Semin could get moved for the rest though I suppose. Seems unlikely though. I think they would prefer to move him to a team who can give them a young piece that could step in right away.
First trade? Sure, why not.