My parents keep telling us that we have to move for US, not them, and to what suits us - they argue that the next generation is more important than the previous one, and they have pointed out that they are quite likely to move from their lovely little village to a town/city as they get older. Why assume your parents will stay where they are?
FWIW, we are moving partly because we are so far from my parents, but the aim is to be within 'return trip in a day' distance. A journey that we can manage with the children, with one driver, with no (planned) stops - 2-2.5hrs is what we've agreed is doable for everyone.
You need to establish priorities - in three or four years' time onwards, is it more important that your DC are able to pop in to see your DPs, or that you have good access to facilities/activities for them? Which journey is more important, the one to your parents, or the work commute? Every 15 mins more that your DH adds to his commute is 2.5hrs a week less that he sees the DC. Same for you, if you get the job, so 5hrs less total pw with parents.
If your parents need you more, they'll move, especially as you're an only.
Seriously though - if you lived 30 mins from your parents, and they're in an isolated area, how far from work would you be living (assuming you both find new jobs as presumably your DH's new job would be too far)? 45 mins? 1hr plus? In the other direction?? And you think that you'll finish work at 5, drive 1h30 to pop in in your parents, drive 30 mins back home and pick up the DC at 7.30ish from the CM or wherever? You need to work through the options logically, they May not be options after all, and then you'd have no regrets.
We've done the same calculations, we got a big map and drew various circles. Living close to my parents sadly just isn't workable for us - they live in the wrong place, not us, and careers, schools, local facilities like handy shops, leisure centres, doctor, etc, children's social lives, children's independence as they grow older just aren't worth sacrificing for in order to live within 30 mins of my parents... Who are often off on holiday, visiting friends and generally enjoying themselves anyway!