For many years I carried the 18-200 and a Sigma 10-20 and some polarising filters as my go-anywhere kit with a D300. It was mostly used on weekend backpacking trips in the mountains. The 18-200 was used for about 90% of the shots and not very often at full stretch (where it is not at its best).
If I had to choose only one lens for a long trip it would be the 18-200VRII. 18-300 has a bit more reach but it is significantly heavier and longer. This is a factor when carrying it on the shoulder strap all day.
Your 18-105 may actually be sufficient for most touring needs. I would say that of all the years of carrying the 18-200, only about 15% of my shots were taken at focal lengths longer than 105mm