We don't live that distance away from our little ones but we don't see them anywhere near as much as we did when we lived closer.
To help keep our relationship alive I send a postcard to each child every week. I supplied them with cards and stamps and they write back, not every week but when they want to.
Even the littlest can do that , or send a picture. They love getting post.
I also send tiny parcels filled with bits and bobs( nothing expensive) , it might be new pencils, a toy car or a pretty lipgloss depending on the child. They love that and if one does not arrive on time they are waiting for the postman daily. They email me that they received them and tell me something about their lives.
It gives us talking points for Facetime or Skype.
I too walk with a stick but I've travelled a lot in the US and they make it very easy accommodating disability , so I say bite the bullet, make the trip- it will be so worth it.