I don't think you mentioned that the area in question is that big in the original post, but in any case, you did say:
That is NOT dangerous to pets?
Personally, I don't even use Roundup especially since some new facts have come to light, and most other broadleaf type herbicides that leave the grass standing (I assume that's what you are looking for) have pretty significant/profound environmental implications --> I.e. Hazard to pets, though plenty of people use them without a second thought.
I suppose another option is to till and re-till the area or use other organic herbicide to kill off everything, but I don't think that's what you are looking for....
Are you really planning to create an acre+ " lawn"?
This is not from experience, but logically, it seems like you could section off the areas and treat them in turn. it would seem less daunting, and this would at least provide opportunity for non-use for whatever period is deemed "safe" after application, though I would recommend you research that point thoroughly before actually spraying.