It's great that you are considering a trip to Galway this October!
The Camping Ireland website
mentions the campsites and caravan parks by county. By clicking on each one of them, you can see their opening dates. I have linked the ones in Co. Galway
for you. You can extend your search to the neighboring counties (Clare, Mayo) if you'd like. Spiddal
Caravan & Camping Park for instance, is open until October 31.
Are you planning to visit Galway and Connemara by any chance? What is on your itinerary so far?