May I suggest you look for their crank radios and flashlights? While batteries are great, our children had a propensity to burn through them. This year we are providing them with crank lights and radios. No worries that they'll run out of the power. The past two years we've had some 15 days of power outages combined. We're getting the routine nailed down.
I should also add that you might look into "personal fans" that you can hang around your neck. We've used them and they've made a difference in August heat. I don't have a photo, but I do know that Walmart carries them.
Good luck!