Should I drain all the pipes before a freeze?
Shutting off and draining the water is a good idea. If for no reason other than an unnoticed leak could cause considerable damage.  Don't forget the water heater and fridge if it has an icemaker since the power is off. Also the toilets, flush them after you have the water off. Then use a large sponge to sop up the water in the bottom of the bowl. Dip the sponge in and wring it out into a bucket. For extra insurance pour some RV antifreeze into the toilets and sink traps.  Use RV antifreeze not automotive antifreeze as the RV type is nontoxic and flushable.  When it comes time to turn the water back on remove all the faucet aerators or they can become clogged with sediment. Run the water until clear before reinstalling them.