It's Spring!
First weekend of Spring so Daddy and the boys are outside getting fresh air while Mama gets in some spring cleaning.
OR
Nathan has cabin fever as he finally gets over his cold, Liam can't nap for all the coughing going on, and Mama is ready for her third nap of the morning, so Daddy and the boys are headed out even though it's snowing AGAIN because it's supposed to be spring darn it.
It's all in the story telling.