If the draft fell the way you say here - - even though I'd be surprised if it did - - I'd take the Atlanta trade offer to go down to #8 and pick up the #75 pick.
The reason I'd do that is because I'd then try to trade the #8 pick to some other team who wanted to move up - - and in the process pick up yet another pick in rounds 2/3 for this year.
If your scenario is correct and I make that trade and ATL takes Peterson, the Vikes are drafting at #7. They are reportedly in love with Gaines Adams (already gone) and Jamal Anderson (still on the board); assume for a moment they take Anderson. So a team that covets Landry (not a position the Skins should spend a high draft pick on) or Branch (not one of my favorites) or Joe Flabeetz would now be motivated to come to the Skins and try to grab that #8 pick... And hence I'd start to rebuild the 2007 draft that was so horribly traded away last season.