I'm on your side.
When my husband divorced his first wife, HIS parents practically took "custody" of his two daughters, 16 and 18. She told them that they didn't have to come to OUR house if they didn't want to or if they didn't like me, that they could go to HER house and still see their daddy.
We played along for a while, seeing his children only at his parents' house; when we realized that it was damaging our relationship with his children, we stopped playing the game and giving his parents that power over us and our relationship with them.
We just dropped out; eventually the kids came to us on OUR terms and now we have a wonderful relationship with his girls and their children, much to the dismay of HIS parents.
I know one thing: I'd NEVER take the side of my grandchildren over our children. EVER.
another aspect...really very sad one....is that a lot of people do not have very involved grandparents...
while I knew and loved and respected my grandparents, my kids and their cousins have a very limited relationship with a certain set of grandparents...
its not a money thing...they have plenty...its not time...been retired since my kids were very little with lots and lots of time.....and its not distance....just a short drive away...
but let's face up to a reality...some people are just selfish in doling out their time, let alone their money....
its sad because none of the cousins have learned much respect for the grandfolks....its their loss.....
otoh......I swear on a stack of Bibles that if God grants my kids children, I will if allowed be very very involved and helpful...with the emphasize on helpful....
young people need our knowledge, our wisdom and sometimes our money lol to get on in life....