Just Bet it, like 1/2 or 2/3s pot. It's difficult that He's unknown, but you can expect people to call that flop with pretty much all of their pf calling range, including overs and all pps. If he raises I think it's a fold with no reads.
I think i'd bet less on the flop too, like $.25-35 is good when the flop is so dry. You just want to get your hand to showdown really, and not show aces and kings free cards.