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?
15 years is quite long, there are new competitive altcoins that appear each year and they competition is very serious. I suggest that you update your portfolio every 3 years, diversify if necessary. I suggest Bitcoin, Ethereum, NEO, Monero, Ripple, Stellar Lumen and XEM for long term and update it after 3 years. So, what would you include in their new accounts, so that they can use it in 15 yrs?