Let me try to clear up the questions

Cindy and Ben had two children. Their daughter Virginia was born during the show's regular run. In the second "reunion" movie, Mother's Day on Walton's Mountain, Cindy was pregnant with their second child. The focus of the movie was Mary Ellen's marriage to Jonesy and the jeep accident that rendered her unable to have more children. Since she didn't tell anyone right away, not even Jonesy, no one could understand her hostility toward Cindy. But being around her pregnant sister-in-law was just too hard. Cindy eventually gave birth to a baby boy, Charlie.

In a later reunion movie, Virginia had died at some point but her age and cause of death were never mentioned. Cindy was in that movie but much older and sadder. Mary Ellen and Jonesy had adopted some children and Grandma was living with them.

In this movie, Cindy and Charlie were not present or mentioned. I don't even think the shed where they lived was part of the set.