The first thing that would happen is that Lynn would retcon who Jim and Marian were. In the original version, the two of them were praised for keeping their grandchildren at arms' length and shutting down any attempt the kids might make to bond with them. Since the role of grandparents would shift from being "people who interfere with my parenting" to "excellent people like me", their wonderfulness would express itself as being a second set of parents.
Next, we have to contend with Lynn's need to state that outsiders are always scary and wrong. This would surely take the form of Lynn becoming the exemplar of giving her grandbabies toys, time and attention while Mira and Clarice Caine would be the ones who would sit on their arses drinkin'coffee while Elly's grandchildren played in traffic and drank drain cleaner.
We could also expect to see Elly and Connie whine about how Elizabeth selfishly and irrationally followed the bad advice of selfish people who don't want Elly to win even once by not letting Elly swoop down and give her grandchildren the attention she never seemed to want to give her, Mike and April when they were growing up. Any sort of indication that this is in any way hypocritical on Elly's part would be explained away in a silly, self-serving fashion that whines about how adult children should just get over being treated like monsters who want to destroy their mother because said mother no longer believes that to be the case decades afterward.
Finally, the baby would love Elly more than any other character and would regularly spit, tinkle and defecate on John Patterson. That'll teach Rod to want to try to be a part of his grandchild's life!!