Been looking for a 18-200 equivalent for Canon myself that is both light weight and having a good coverage... was at AP asking the question... basically Canon does not have it. The sales recommended Tamron AF 18-250 mm /F3.5-6.3 instead. Seems to be a relatively cheap and good option. You may want to check out the reviews on the net.
If you don't want the hassle to keep switching lens when you travel; I hate changing lens while traveling... by the time you change, the scene/subject is gone.... and you risk the foreign particles getting into the sensor and you can't get the sensor cleaned while traveling...I would think 24-105/F4 gives a good coverage and F4 is a plus for museum, indoor, cloudy, etc.. while traveling.