If the $100 charge is 4x$25 for 4 segments, that's actually pretty good -- some of the other legacy carriers (AA, UA) charge a lot more. If the nonstop gives everyone peace of mind, and that's the only option, I'd just go with it and pay the extra.

Btw, any particular reason to think the 14yo couldn't handle navigating the airport alone for a plane change with a cell phone to call someone in case he gets confused? Is he a particularly timid or inexperienced flyer?