I know what I would do: exactly what I am doing now!
You see, if I was God, I could do anything, so I would try to live my life in different ways to see which way would be most exciting, interesting, pleasurable, whatever… Then I would likely come to the point where I would also like to live completely different lives. Quickly, I would discover that I can live several lives in parallel and compare… From there, it is a quick step to actually living every life around and enjoying all of them! Of course, I would actually have to make sure that while I am living the life I would not know that it’s all me, because it would quickly lose any sense otherwise, would it not? All of me would pretend to not know anything about Me and get on with life to only get reconciled eventually after living the life.
So, yes, if I was God, I would be living all these lives simultaneously, in all this huge universe, and enjoying it all in all its diversity. I guess, I am doing it already. Cool, eh?