Yeah, kolsch yeast will work well I think, and I've reused yeast cakes before. If you can keep the temps on the lower side, it will help it have that nice lager-like clean flavor. Also, you should take half the cake out. There is a growth phase that yeast has that it will not experience and I read somewhere on here that it could lead to off flavors because of that developmental phase, they eat and act a certain way and reduce certain off-flavors when they are spending a certain amount of energy multiplying.