Hi and welcome to the Chiari forum,
Chiari symptoms do cycle and with the crazy weather we are having this winter it is even affecting those of us who have had surgery.....
Surgery is only needed if he has a CSF obstruction....Surgery does not always eliminate symptoms...some mayb, but ALL, not something to have surgery for....
Make sure u have a true Chiari specialist and they do testing to rule out ALL related conditions and even non related so u know the best course of action.
I know it is not easy to see ur child in pain, but try and find out more about how his Chiari is affecting him and his overall health first.
I don't have any advice as I was diagnosed as an adult (of course looking back had symptoms since child hood) but I wanted to offer you support. What a scary thing to go through!!! CSF flow would be a determining factor I am sure but quality of life would be so important to consider as well. Good luck!