I am a 65-year-old taking care of my 98-year-old mother and a 14-year-old Grandson with no support.

Use moms money to hire in home help to give you respite. Where is your grandsons parents??? How did you get to care for this child w/o support?

You don't give us much to go on here, but I do hope that your mother is now being taken care of in a nursing facility, so you can just be her loving child and advocate and not her burned out and overwhelmed caregiver.
And that should free up time for your grandson, who hopefully is involved in the many classes and programs that are now offered for children with autism even during the summertime.
And God forbid your mother hasn't been placed yet, then you can call your local Area Agency on Aging or Senior Services to see what services may be available to you. Or hopefully your church has some volunteers that could come out to help you.
You matter too in this equation. Please don't forget that. So reach out to whoever you have to including perhaps even hospice for your mother, to get the help that you need.

Your mother needs to go into a nursing home.

I think that when you decide this is on longer sustainable, you will take action one one front or the other here. Until then you truly do have my sympathy.

You have a lot on your plate! What kind of help do you need most urgently? Financially? Emotional? Respite? Etc contact your county�s social services to ask questions and maybe get a caseworker. Are you your grandson�s guardian? Who is PoA for your Mom? They will each get their own caseworkers from the county.