Nikon 18-200 mm or 70-300 lens for sports?

I'm looking at upgrading my camera (I currently have a Nikon D50 and want to get a D7000). I currently have a Quantaray (I know it's cheap, but what we could afford) 70-300 lens, a Nikon 18-70mm and a Nikon 50mm fixed lens. I take a lot of pictures of my girls soccer games and just a variety of family pics or food pics for my blog. I'm looking at two different kits (this seems the best way to go for me). One has the Nikon 18-200 lens, and the other has a 70-300 and 18-105. I hate to lose 100mm if it makes a huge difference when shooting sports. I'm just not sure what is the best route for me to go.

For shooting field sports, the 70-300 mm may be a better choice if you do NOT plan to move around the field sidelines.

I have successfully use the Nikkor 18-200 mm lens when shooting motocross and field sports, but my favorite lens is the Nikkor 300 mm f/2.8.

18-200 mm lens sample

300 mm f/2.8 lens sample

Shooting at night will require a faster lens

As you can see, shooting sports requires a substantial investment in lenses. The D7000 is a good choice of camera

You already have a 70-300mm lens that should be good enough for sports. It would be a lot cheaper if you just got the body without a lens. The games should be played outdoors under lots of sunshine so the D50 should be able to handle that easily anyway so personally, I don't see a need for a new body.

Although the D50 is slightly old (in dSLR terms), it's not THAT old. I don't see why you feel the need to upgrade (a maximum burst of 12 jpegs is plenty for recreational photographers taking pictures of sports).

Unless your quantaray has noticeably bad quality, I don't see any benefit in getting another cheap 70-300mm lens (as I'm assuming the nikon is) - a $160 lens is probably not much better than the one you have now. Generic lenses have come a long way since the early days, what with modern computerized manufacturing processes.

I would rather spend money on a fast telephoto lens (fast meaning a low f-stop number like f2.8)

but if you feel you must, I personally would go with the longer lens for sports. Although 200mm is o.k. (depending on how far away you are), 300mm is probably better in this case. I think it makes a difference.