The D100 will not focus as fast as the F100, thu it's not bad. The D100 has a buffer to store shots, so it will be better than the cooplex. It's not perfect but it's a step forward.
Is the D100 a good investment, I suspect in your case no. It sounds to me that changable lens is not a requirement and a compact camera is what meets needs.
The spec for Nikon 5700 has a 70ms shutter lag and can take 3 shots a second upto 10 frames. I sure there are others too look at.