I think you're first choice was the right one.

To operate in lowlight indoors you will need a very fast lens to get a bright viewfinder image and for focussing. You will not better the 50mm prime lens for sharpness and contrast they have a huge reputation for it, having been refined over so many years as being the standard lens for slr film cameras. I have no experience of the Nikon 50mm yet I have heard others (professionals) say it is superb which is exactly as I would expect. The crop factor on your D200 turns it into an effective focal length of 75mm which is just about ideal for portrait work.

With a slower lens, be it zoom or prime, you will find the focussing is slower just when you need it to be very fast and accurate to capture the moment in difficult lighting conditions. Go with a longer focal length and you are also limiting your dof which will make the focussing that much more critical - double whammy !

 

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html