Froggie, one thing's for sure: Even if you lose some of your independence and physical abilities to this illness, you'll still kick ass like no other frog I've ever met.
It's tough to think about so many changes at once and I can totally see how it must feel like an overwhelming avalanche of loss, loss and even more loss. And, no doubt, things will be lost. Important things. And that sucks. But some will remain and others you will gain back by finding new ways of doing them. Isolate the need from the way of adressing it; one has nothing to do with the other. There are so many ways of being there for your grandkids and of staying in touch with nature. I'm sure you'll find them :)