Well as a Hyundai/Kia tech let me start off by saying that most likely you will never damage a piston with a valve. Its the other way around. The valves are weak, tiny pieces of metal that will easily bend when the force of the rotating assembly pushes against it.
What you see in the top of the piston is far too perfect to be valve damage. What you are looking at is valve reliefs. These are pockets machined into the surface of the piston to make room for the valves. The valves actually open up into these reliefs. 999 times out of 1000 you will never do any significant damage to a piston from valves hitting.
You will be ok reassembling that engine with a simple valve replacement.
BTW, here is what a Brand new piston from a 3.5L Sedona looks like.