From what you are telling me, your child would certainly meet the criteria used by the IRS to determine if a child is disabled.  You may want to get something in writing in case you need it in the future.  The following passage is from the IRS and I have included a LINK below where you can learn more.

"Proof of Permanently and Totally Disabled. To prove your claim of EITC for a child who is permanently and totally disabled, you need a letter from the child’s doctor, other healthcare provider or any social service program or agency verifying the child is permanently and totally disabled."

https://www.irs.gov/credits-deductions/individuals/earned-income-tax-credit/disability-and-earned-in...