I think the best way to hand that stuff off to your children is to wait until they get to a point where they hand off can happen, when they are adults, and then hand them a highly curated set of photos on a USB drive and let them do with it what they will.

The key is in the curation though, it is unlikely that your child will want to sort through thousands of blurry, duplicate, or unrelated photos. 100 really good and special photos/videos are better than a mixed up mass of 5,000.

If you are concerned with passing away before your son is of age, just make sure there are multiple backups, and the sign in information for anything that isn't local is communicated to his guardian.