That thought occurred to me, too, but the family they are staying with are too young. The parents are only in their 30s, and their oldest child is 14. The head of the Sherman household and his wife are in their 60s, and it looks like their oldest son is probably married with his wife in the household, too, and I think the two Shermans in the Coursen household may be their children.
The younger Sherman husband and wife are roughly the same age as the Coursens, and I could see them leaving their young children with Mrs. Coursen for while. Maybe the young Mrs. Sherman needed to go buy groceries or something. ;-) (or maybe she just needed a nap!)