Crede has no trade value at all right now. He's never done well in the past, and he's not currently doing anything special. The daily double. Nobody is going to put him in their starting lineup unless they have no other choice.
So any trade you make would be for Beltre only. Because he's hot, you could possibly actually get someone to trade for him. However, as good as beltre is doing, he's still a free agent in both of my yahoo public leagues.
Unless you run into a stupid owner, I wouldn't attempt that trade for anyone except an injured Furcal, Rollins, Lugo, Cintron, one of the Alex Gonzalez's, or another mid to low tier shortstop.