Hi, I hold a few tokens of varied nature and a few coins. I have setup a few eth addresses for the younger members of my family. I am talking about kids that are less than 3 yr old

So, what would you include in their new accounts, so that they can use it in 15 yrs?
Every year there are new coins with new technologies. Trends are changing too fast. Nobody will ever give you a good answer. I would say there is no currently such crypto that could be used in 15 years. Perhaps only ETH.