In my case the "other" local granny is at least 10 years younger than me and does things with them that I am unable to do: hikes, trips round the shops etc. I have always done quieter things with them: reading, board games, craft etc. It is a nice balance.
When it comes to being here, I only have them for very short periods, e.g. pick them up from school and, give them tea. When the GC from away come, they stay with one of my local DDs as they have the space, and also it means the gang of cousins can play together, which they love.
In any event I cannot see myself coping with them staying, although of course in an emergency they would be welcomed.
I do find it very hard work when they are here - I love them all dearly, but they move too fast for me and make too much mess! I am on crutches at the moment and fear I might simply get knocked over!
So don't feel bad about finding it hard - we all do - we are getting older!