Op, I can understand the issues on logistics. That’s an aside really.
the bottom line is that your son seems happy with then childcare arrangments he has. Both parents do. The only people who are irked by this arrangement currently is you. Because you’re not seeing your grandkids as much as you used to, or want.
i think you need to put it into perspective. You have had the privilege of being in your gc lives a lot to date…it sounds like a huge amount. That is a privilege, really. Lots of people simply don’t live close to their grandkids because people have to move to where work is . Whether the Gp ’s would like to have a closer contact with gc is irrelevant..it is simply not logistically possible. BUT it simply doesn’t the. Follow that these GPs don’t have close relationships with their GC.
also when divorce happens, it is a massive shock to the parents that their access time is split and they don’t get to see their kids as much. Your son has them just one night term times (reasons not relevant), of course he doesn’t want to loose that time by handing kids to you. Same with mother. Fgs, I divorced after 30+ years of marriage and my “kids” were adults living a long way from Home for work. It was a massive shock for me to realise that I’d see them even less than before, because their precious annual leave and weekends that they had free to visit parents, were now being split between me and exh. I simply didn’t think about that until post divorce. So, everyone has to come to terms with that concept that a massive change is happened, and whatever is agreed around childcare EVERYONE will see the kids less. And the priority for the kids , particualrly while they are still adjusting to not having mum and dad around jointly all the time, is to maximise time with both parents. Then siblings if that is an issue. Not anyone else.
You seem “stuck” in a mindset of not wanting to accept that change. You want to keep things as they were in terms of overall contact time (or at least maintain that frequent contact). It just isn’t in kids best interests, nor is it in your son and his relationship with exw interests to push this.
imho, you need to start thinking outside the box. Do the things that 100000 of GP do all across the world, which is to look at other ways to maintain a close realtionship even where you can’t have direct contact. Arrange with mum , if possible, that you have a FaceTime call with kids for 20 mins once a week. If kids are still young, offer to make that their bedtime story. Send kids random letters, pictures, postcards frequently….young kids get excited about receiving something in post…create a special “tradition” with them that is unique to yours and theirs realtionship (my MIL and FIL were excellent at this with stuff like sending Easter eggs for their Easter egg hunt, sending silly post cards they’d find in their home city, FIL following football teams my DSs followed and calling after each game to discuss…) . There are so many ways you can actively promote and encourage a strong relationship even if you can’t always be face to face.
Remember , they aren’t little children forever, once they hit teens they’ll probably want to hang with mates not go to grans house after school even if you did have access to see them, but if you’ve already established lots of things thst can be done remotely that’ll mean it can be kept going. And the skys the lint once they’re old enough to have phones. My niece and nephew have amazing relationship with their grandma who has always lived 250 miles away. They’re young adults and love her to bits. She’s 90 now. She made huge effort to use technology to do that, video calls, silly letters etc etc. my dc did same with their grandparents (my IlS , both my parents passed away far too young ) mainly through old fashioned snail mail and telephones, and they’d always have the kids for 2 weeks during summer holidays which was fantastic for them and us!
I’d also be very careful at comments re the mum. If you want a relationship, you need her trust and support to allow that to happen on her context time too. If she gets a hint you’re slagging her off (as you have here) , game over for asking for calls etc while there in her care. It is highly damaging to have that attitude, and completely cutting your own nose off. Reach to her to offer the gold dust that is cover for emergencies - emergencies happen all the time with families…kids get sick and can’t go into school at short notice , someone needs to go to hospital for that suspected broken bone and not want to drag other kid there for 5 hour wait, other childcare fallen through, teachers training days…all of these are options for the mum to call and know she can rely on you to step in with no judgements, grudges…
kindly, you need to accept that things have changed. You can’t turn back a clock. You may even find it helpful to look at “grief pathway” and understand a little about why you feel angry towards mum in this matter (the bitchy comment that she is only doing it for money is beneath you frankly - you can’t tell anyone what mum is thinking and feeling). It may also help you to understand that this huge change has impacted you too, and you need some time to emotional process the “new world” and accept it, and then make change.
look forwards positively. Use your skills to think outside the box on how you will encourage a close relationship in the new world there is now.