The 14 year old can’t fly without someone who is at least 18. So you’d have to pay the UM fee, right? He (and his brother) could fly Southwest or Jet Blue (they have lower age restrictions) but both those require a change of planes and have really bad flight times. Jet Blue flies into DCA. Southwest would change in Denver - 6 hour layover. BUT it would be an adventure!

EDIT TO ADD that SMF has better options than SFO on Southwest. Still a change in Denver but just 2 hours instead of 6.