At this point, I'd take Butler over Pena, Price over Granderson, and yes, you can get Jenks on the cheap, but remember, his manager is Ozzie Guillen and with him, hell, he could be a spot starter by next week. I like the idea of trying to put low, and even like the buy-low options, but I think that you're giving up too much.
How about the following counteroffer. The prices are their prices protectable for next year:
David Price (19) Brandon Morrow (6)
FOR
Curtis Granderson (24) Bobby Jenks (12) Ervin Santana (6)
I am giving up the best protection (Price), but is he going to be better than Granderson, who would eventually replace JD Drew, Justin Smoak, or Carlos Quentin in my lineup, but am I getting back enough offense for this year?
I would go with the players that help you weakness if its 5x5/roto. I am not sure Nathan will be great for the first half of next year (he will be good but prob not Top 5 closer).
Prince has a ton of potential and getting granderson for a 24th is nice. However, I am not apposed to getting Pena unless he kills you AVG too much. He def helps in HR and RBI.
Who are you remaining pitchers? If you truly can spare Price, then it seems like a decent deal. That said, I would be hesitant to trade Price as he looks to be breaking out!