Does anyone have any knowledge of right of first refusal vs. grandparents rights in CA?

I have agreed to 50/50 with my ex because he promised to be involved in the children lives in the future but now it looks like he's roped in his parents for the long haul to hold up his end of the deal. The children saw them at most once per year and they still get upset about spending significantly less time with me (I was the primary caregiver throughout the marriage), still little time with their father and lots of time with people they are not used to.

I have to budget my time with my lawyer carefully so I thought I'd bounce the idea around here and see if anyone has any experience/knowledge in this.