Sue,
The D90 has the same sensor as the D300 and has pretty good higher ISO capabilities.
If you expose the picture correctly and use some noise reduction software, your should be able to shoot at ISO 1600 and get good shots. If you even get a picture that you really like but has more noise than you would like, covert it to B&W and notice how the noise adds a nice grain look to you pictures and makes then very usable.
When shooting on a tripod you can bring down the ISO and let the camera expose for you with a longer shutter speed. Might want to use a timer so that you don’t bump/move the camera when pushing on the shutter.
Loose sharpness when using a zoom? Well....yes and No. As a general rule Prime Lenses will give you better results. Even inexpensive (Kit Lenses) have a sweet spot and can still take great pictures.
Much more to talk about......
Problem is, finish9's kids want to shoot sports, so you can't use slow shutter speeds. What's worse, they're talking about indoor sports. And even though they're indoor, they'll still need something on the order of 100 mm for most shots (35mm film equivalent focal length).
No substitute for big aperture and sensitive (high ISO) sensor, unfortunately. Even image stabilization and a tripod will be of marginal use. The only other thing that could help, as another poster has said, is a good flash, at least for subjects closer than about 40 feet.
Any way you cut it, it sounds like $$$ to me.
Thanks for info. I will try using the timer—I forgot about that trick...I think it is me moving the camera. I have gotten some very nice photos so far, but I am also ruining some. They just are not in sharp focus. I try to use the Prime lens the most but on tall buildings and when I am so far away, I can’t. I have been using the auto focus....I think I will experiment with manual controls. I do have time but will have to know what I am doing :( .
I just got a new MAC with photoshop, etc. I will have tons of fun I am sure messing around with my photos. It is nice to start out with nearly perfect ones though. I do like grainier pictures in some instances though, esp. in construction shots.