That is what we did for our move from Chicago to Clorado Springs. I kept the car around 78* using a/c durring the day and heat at night (we moved in October ). I had a temp gun to check the temps periodically. We stopped half way at a friends house. I placed plug- in heat pads on the sides of the sterlite tubs at night. The temps stayed around 78-80. Also be sure to keep the sun off the tubs. I used a bed sheet to cover them since we have a hatchback. Also don't put the tubs directly on the floor of the car. Heat from the exahust can raise the temps and it can acctualy cause fatalities.
Sorry for the spelling...typing from my phone. :/