I pitch all my beers at fermentation temps- 65 degrees for ales, 50 degrees for lagers. Some people do pitch their lagers a bit warmer, though, to ensure fermentation starting. In this case, I think the kit instructions are to help people get fermentation going, so you can follow those the best you can. I would lower the fermentation temperature 5 degrees per day (10 degrees over two days) as to not shock the yeast. When fermentation is finished, you can raise to room temperature for the diacetyl rest. I rack after the diacetyl rest, and that's when I start the lagering process- I lower the temperature 5 degrees per day until I"m at 34 degrees, then lager the beer for 6-12 weeks.
Your yeast should be fine- but make sure you do a starter first to ensure it's ok and to make sure you have enough yeast to get fermentation going.