Road trip with solar panel between roof rack...

Hello Forum! I'm planning a 8000+ miles cost to cost and back road trip this August. It is going to be Me, Wife and 2 preteen kids. I'm going to camp most of the nights and though about how I can make this trip as comfortable and convenient as I can for them. I had several ideas that came across my mind. One of them include mounting a 250 watt solar panel between the roof rack of my 04. I searched around the internet and didn't find any Sienna owner posting about mods with solar panel so I'm starting one here.

Why solar panel??? I was thinking that I can run a chest freezer and bring frozen food to the camp sites. I'm not sure if I will proceed. If I do, I will only need to get a few parts and the rest, I already have.

Parts:

• 250 watt solar panel - ~$400 Amazon
• Solar MPPT Charge controller - ~$100 Amazon
• 12v Batteries - I have 4, 12v, 75ah but 2 is probably sufficient for my needs
• Inverter - I have a Xantrex 1000W sine inverter
• Cables - I have 50' roll of 4 gauge cable.
• Chest Freezer - I have a 5 cf Kenmore. It may take up too much space. Considering the following smaller ones
  • Danby 3.6 cf - ~$200
  • Avanti 2.1 cf - ~$200
  • Whynter 65 Quart - ~$500
  • ARB 63 Quart (splurge ~$900)
• Small Microwave - ~$100
• Fan-Tastic Vent - Not sure of the cost and not sure if I want to punch a hole on the roof of my Sienna.

So my question to you Forum is, will this work? One issues that I can think of is charging the battery in the heat when parked under the sun. That is why I consider the vent fan. But I'm not sure if I can install that vent fan on the roof of the Sienna.

My other option is to wire the inverted to car's battery and run the chest freezer when driving. My concern is that there will be periods of time where I won't drive much for 2 to 3 days. Will stuff stay frozen in a unpowered chest freezer for 3 days in a sun heated car?

My other, other option is to run off 2 (or 4) of the 75 ah batteries that I have and charge those battery when driving. But is it safe to run a chest freezer off batteries in the heat of a closed car (probably up to ~115°f)?