The noise in the sky doesn't bother me. However, if you decide to make a big print...
I've had to come up with some unique recipes for dealing with nighttime scenes shot with my Olympus 43 cameras. I've tried Topaz Denoise 5, and I think the results I get in PS are far better. And, I've found that there is a fine line between too much noise reduction and not enough.
For example, to mitigate the noise in the sky, I'd flatten the file so it's only one layer. Then duplicate it and convert it to a "smart layer," Add gaussian blur to the bottom layer--not much, maybe a pixel or two or three. Then add noise (color gaussian) 1% to 2% usually works. And finally, apply .5-1.0 gaussian blur.
Now go back to the top layer, create a mask, select the sky fill black (or any neutral shade) and see how it looks.
I like leaving the bottom layer a "smart layer" so that it can be re-edited to accommodate a range of print sizes or web resolution.