Why would your grandchildren want to view several thousands of your photos? Just find the best ones, and backup to multiple locations. Print the best of the best and make a physical album. Scribble some notes under the photos with an actual pen. Your grandchildren will love it. By doing that you are giving importance and meaning to the images, which otherwise would be absent in an ocean of dropbox archives.
Hwo would your grandchildren be able to view outdated digital file format that no one knows how to use anymore ?
They'll probably be busy trying to find clean air, clean water, food and shelter scrambling to face the consequences of overpopulation in a climate changing world out of cheap oil more than looking at photos they don't care. You don't even look at your own photos from a few years ago.
The best for which purpose? Your descendants will probably not be looking at your pictures with the same ends in mind as you (if they are looking at all).
