One other factor to consider is air quality due to wildfires. It's (another) bad fire season in California, so you may need to close up the windows and run the A/C to keep cool, and may end up needing to use the A/C more than you expect even if it cools down in the evenings. Air quality can vary dramatically from hour to hour, you could be in relatively clear air in the afternoon, then have unhealthy air by evening.
I'd bring along an air purifier to run in the RV, but with young children and the number of active fires, I'd even consider cancelling the trip.
Here's a good source for air quality information:
https://www.iqair.com/us/usa/california/siskiyouThey do make forecasts for a week in advance, but I haven't found them to be very accurate for more than a day or two out, so even if the air looks good (or bad) for your trip in the forecast, it may not turn out to be as forecast.