Hi Caleb--
I've got some thoughts I've been compiling on the subject of pain and nutrition for the past few months. Note that these don't specifically apply to cerebral palsy, although I should probably do some research into that and other nervous system conditions.
No doubt you already eat low omega-6 and sugar. Have you tried the ol' paleo standbys like drinking bone broth and avoiding nightshades? There are some other more creative things to try as well, like cetyl meristeolate derived from the green-lipped mussel. Also, maybe some different sorts of physical therapy exercises/modalities could be helpful. Have you ever heard of low-level laser therapy? It didn't do anything for me, but has helped others.
My overall thought is that there is a step-wise list of things to try, and there are many things out there. The problem is that they cost money. Whenever I get around to putting the above-referenced site up, it would be cool to order the treatments by price:efficacy ratio.
Best of luck!