They stopped giving presents to their married children. Single children still got gifts for obvious reasons. They gave something to the young grandkids, but as more arrived (and they got older) they gave a Christmas ornament each year. The last couple years they have given family history, stories, pictures... and everyone is happy.
Nobody resents their grandmother (my dad passed 5 years ago). You seem more angry than I think your kids will be. The tithing/"sitting on billions" comment was a bit odd, but we all have different takes.
My grandmother was great and didn't give Christmas gifts each year. We just stayed he night at her house.... (my father's parents passed away in their early 60s and my mom's dad died in a car accident in at the age of 54).
Note: Two of my kids got married this year. It may be the last year we give them stuff.