Well, if you want to have something for your kids to be there in years to come, the safest bet would be the mother of all coins. Obvious BTC is obvious ; )
With many people suggesting it will be 10,000 or 100,000 or even 1,000,000 USD in the future, that should be good enough. Even if ETH or others gain more on the short term (and maybe crash to 0), on the long term BTC will be there for your kids.