I was in GIG back in Nov, arranged meet and greet through hotel and it was easy to spot driver with your name or hotel name holding up a placard when you arrive. Would def recommend this, with mobility issues you can also request wheelchair assistance and they will guide you through the aiport. Brazil is very accommodating with special lanes for mobility issues and the elderly. If you don't arrange this through hotel you can do it on viator.com or getyourguide.com

I'll add that Ubers are indeed inexpensive and easily available, however they are very different standards form what I am used to. Always ordered the most expensive ones and they were all what I'd consider a compact entry level SUV, clean and safe though. I didn't feel comfortable/safe walking anywhere, maybe a block or two form the hotel in daytime but that's it.