Toddler and 1 month old

I live in Oklahoma we’re the weather is 100 degrees. I have a toddler and a 1 month old. We are outdoor people and my toddler would live outside if he was allowed.. but my question is how do I manage to go outside with my toddler but keep my newborn cool during the day. I try to go outside with both of them in the morning and late evening but sometimes that’s not enough for my toddler lol. I have a friend that has a baby about the age of my newborn and she puts a bassinet next to the the back door and carries a baby monitor but it makes me nervous leaving my little one inside by himself at such a young age. So again my question is how do I keep my newborn cool?