In my opinion, this situation, like all others, can be seen from different perspectives. Whatever behaviors you exhibit as a result of your son's decision could be misinterpreted by your daughter in law and/or her family. How close do you want to be to your son and his family? Your son is a grown up man, not your baby. This is a very sentimental thought, but not reality. Baby days are over!!! He makes the decisions. Painful but very real.
You sound like a strong person. Continue to get support from every source possible. Pray, if you are into that, it will make you stronger. Remember that its better to be in peace than to be right.
Thank you for sharing. So many of us face similar situations.