Yes, because you can let your kids use the machines at ages that would scandalize the urbanites (check the laws for your state, you find things like "twelve year olds can operate farm machinery incidentally on a road or highway").

Not as much, but once you start mechanized farming you don't need many people in agriculture. There are few enough farmers in industrialized countries that they don't affect demographics much.

My sense is American farmers have more children than the population at large, but I don't have numbers to back it up. My farmer maternal great grandparents had 12 and 9 children -- I don't think that happens much anymore.