The never-freezing but always cold garage will be perfect.

I layer my cannas with large perlite and leave the plastic top off. I've found a large plastic storage tote is convenient - but remember that even with using perlite, there is going to be some weight, so you might want to use a middle size. Since I started using perlite around each tuber, I've never lost any to rot.

Remember to label the box, and don't forget to start some or all of the tubers in late February or early March, so that you can plant them outside in early spring. They take ages (6 to 8 weeks) to come out of dormancy, and seem to be very tolerant to living in a gallon jug until their real soil is warm enough for them to be planted outside.