Question regarding Prometheus

Hi everyone. My name is Ralph, and I'm new to this forum. I have some questions about Prometheus.Based on the ancient illustrations that were uncovered early in the movie, it seems that the Engineers left instructions for some of the earliest civilizations on how to find what I thought to be the Engineers home planet, or their galaxy. The early illustrations show the Engineers with early humans, pointing at what looks like either a star constellation or a galaxy in the sky. However, when the drawings are eventually discovered and the instructions contained therein are followed, the humans were lead to a planet where the Alien creatures were being created, obviously to wipe out humanity. Now, the early instructions reflected in the ancient drawings -- were they instructions to humans on how to find the Engineers' home planet, or how to find the planet where the Aliens were being created? Did the Engineers already know many years ago, when they communicated with early humans, that they (the Engineers) wanted to wipe out the human race? Or were those instructions originally intended to invite humans to the Engineers' home planet once humans developed technology to travel into space? I wasn't sure about that. I guess I'm not sure how long the Engineers were planning to wipe out the humans? Were they already planning to wipe out humans when they communicated with early civilizations, as reflected in those ancient drawings? I wasn't sure if the early instructions were originally intended to invite humans to the Engineers' home planet, or whether they were intended to lead humans to the Alien factory to meet their demise. My second question is, if the illustrations were originally intended to bring humans to the planet where the Aliens were being made so the humans could be killed, why wouldn't the Engineers simply wait until the aliens are all created, and then bring / send them to earth and wipe out all humans, instead of instructing humans on how to get to the planet where the aliens are being created? From the perspective of the Engineers, it doesn't make any sense to invite humans to the planet where the aliens are being created because it wouldn't ensure that all humans would be wiped out. Only the humans who visited would be wiped out, so this doesn't seem to be an efficient way to kill all humans. Maybe I'm missing something that was pointed out in the movie, but the stuff i listed above had me a bit confused from the outset of the flick. Can anyone clear this up for me? Thanks :)