I won't address the QBs as it seems like that one doesn't matter to you. I think you are giving up quite a bit in trading Jones for Hightower. Don't get me wrong, Hightower has looked good, but Roy Helu looked really good last week and could start to steal carries from Hightower. Shanny has a history of platooning backs (but I suppose he also has a history of riding the hot hand, see Davis, Terrell). Additionally, Hightower has had fumbling problems in the past (he hasn't yet thankfully), but if those rear their head, Helu will get even more carries (Helu had zero fumbles at Nebraska...never fumbled there, not once). Felix essentially will get all of the carries (when healthy of course).
As for Pettigrew v. Nelson, I am curious as to who your other WRs are. I think Pettigrew will eventually get his as teams start to roll coverage outside towards Burleson and CJ.
Ultimately, I suppose if you need the WR help, you pull the trigger, but if not, I would look for a little more because he is also getting Schaub, which is an upgrade at QB for him over Henne.