It really depends on who is projected to be available. If you stay pat, you get to pick 18th overall (likely better then that because other teams likely won't get a first rounder either). If you trade, you get the 12th overall (again, likely better but we don't know those specifics) So, look at the available players. Who do you project to be picked between 12 and 18? Is drafting in the 12 slot a significant improvement over six spots later? If so, consider the trade. If your projected 18 is comparable to the 12 slot, it makes no sense.
In re-reading your question, it seems you would keep the draft position? So, you would keep the 12th slot in all rounds? If so, the answer is pretty much the same, except If you get the 12th and 13th overall as opposed to 18th and 32nd. If that is the case, I would go for it.
Sorry if this is a bit confusing of an answer. Wasn't certain about the trade specifics.
Help with mine? viewtopic.php?f=26&t=453983