A couple little things I would add, which could probably be debated:
First is to try to shoot right under a street light, or whatever better light you can find. What may not look like a huge difference in light to you may make the difference between keepers and unusably underexposed images. As long as you're shooting RAW and set your WB to tungsten, you should be able to recover from the weird sodium light color.
Also, personally, I'd use the 18-200, since it's not any slower than the 18-55, but the compression should help blur out what is likely to be a busy background, if there are lots of spectators where you are.
Finish shots are great, but if you can get shots at the start, too, you'll likely have a little bit of daylight left (at least where I am, I suppose that could vary), and the runners won't be as tired, so you'll get better looking faces (and form, really).