Ask your son. My parents sold and moved when I was a sophomore in HS. 8 miles away. I continued to bike daily. I hold no bitterness and resentment toward them, but a big part of why is that they discussed it with me and asked my opinions. They explained their reasoning- my dad thought housing prices would go down soon. He was right. They sold near the top of the market, doubling the value of the home over when they bought. It's now easily 1/3 less than when they sold. Far from being resentful, I'm glad they made the choice they did, to ensure their future financial security and help prevent us kids from financially supporting them in the future (I would, but it is really nice not to have to).
Anyway, your son is old enough to understand finances, or he should be. Talk to him about the what and the why. Listen and weigh his answer. That isn't to say go along with whatever he thinks, but involve him in the conversation. He's a stakeholder, and his views might surprise you. Good luck!