IIRC Kölsch is lagered at 40oF for 4 weeks. 45oF will be fine.
This (as well as the other info). I lager in the keg under CO2 at 38ish. My last Kolsch is almost ready (right at 4 weeks lagering). Alas, it's not quite to style since I got a little extra bitterness and flavor out of the hops I used (they were out of Spalt, so I used Hallertau). It actually comes off as a Kolsch/German Pils hybrid. I was even considering entering it as a Pils on a lark.
My current kolsch is very similar. It definitely tasted more like a pils when it was younger but has softened a bit with time. I used 2.1% AA tettnang to get to 26 IBUs which equated to a lot of hops. It has an overall 'hoppiness' that is not present in a traditional kolsch. I overshot my gravity quite a bit and decided to add more hops as well and overdid it a bit.
To the OP, if you are kegging I wouldn't worry about lagering it before packaging. For me it's interesting to see how the beer changes by sampling throughout the aging process.