I have a day aged 20 months who lives 5,000 miles away. We've visited once when he was 8 months old. Ds uses Skype so we can see dgs grow up. I regularly send little gifts from granny and granda. I.e. A £3 plastic watering can that cost £6 to post.
I do feel like a granny to him.
But it is definitely different to the 2 Dec who live locally. My joy with the local dgc intensifies the distance from the one far away.
However,Skype will ensure that our faraway dgs is familiar with our faces and our voices so we are not total strangers when we next see him.
I feel that 100 miles is workable for hugs and cuddles. It would be a two hour drive, a day out. Take a pot of stew and crusty bread with you for all to enjoy on arrival so no time or expense wasted on lunch.
I'd guarantee that DH and I would make the journey as often as was agreeable with everyone.
Or meet half way for lunch (picnic in the park) where little ones are not bothering diners. That's only a one hour drive, spend a couple of hours catching up, and then back home. A lovely way to spend an afternoon.