Perosnally, if I am going to be transporting a keg I use one keg as a bright tank (like I said above, I shorten the dip tube by 1/2 inch) then via a jumper rack the beer off to another keg. But I just don't like racking beer into a tank filled with oxygen. I suppose if you could at least purge the ehad space in the secondary carboy with Co2 you should be fine.
You say lagering for 6 weeks in primary - just so you know, that's not at all what I am talking about. If you pitch enough yeast your fermentation should be done in about 7-10 days. Resting it around 68 degrees will help finish it out completely. Then you can rack and crash cool. 2-3 weeks is all it should take. So your kolsch should be done between 2-5 weeks from brew day.