Loading multiple little ones into a car

Hello, I'm wondering if anyone has tips on safely and efficiently loading multiple little ones into a car. Many places have laws about leaving kids in the car for even a short amount of time. How can I safely load a toddler and a baby by myself when I can't carry both at the same time? Is it okay to leave one in the car for a moment when running back inside to get the other? I feel like it's more dangerous to try to take both at once when I don't have enough control over the toddler to do it safely. How do people with more than two do it?? It's hard enough with two. My toddler is unpredictable and has been trying to run off lately.