Beware outdated content
I love having my kids watch this show because the themes are so innocent and because there's really no violence or sexual content. However, beware some outdated themes and ideas--I've found i have to watch with my kids and be ready to turn off the episode.
For example, we watched an episode about an African American character, Joe Kagen, who was trying to get the townsfolks' "permission" to attend church (which takes some debriefing with young children to begin with). The two main male protagonists (Pa and Jonathan) were of course on the moral side of the episode's message, arguing on Joe's behalf, but Mrs. Olsen, the antagonist, was arguing against it. I was shocked to hear her begin spouting racist ideas such as "those people practice witchcraft, beat on drums, and EAT PEOPLE!" Then, as if that's not enough, her husband, who is supposed to be on the "right" side of the moral message, states that her view is ridiculous and "this is America, not Africa!" So not only do kids hear racist stereotypes that they might not otherwise hear, but then they're told that those things DO happen in Africa! So things like that, which were considered moral and "progressive" in 1979, are outdated, racist, and horribly ethnocentric by today's standards. Just beware the time lag!