Another aspect of this is you die before parents like what happened to a family recently. They only found out he had bitcoin through his banking history and seeing these repeated transactions to a exchange. They contacted the exchange and are in the process of figuring out ownership.
Think how often that is going to happen to bitcoiners when the majority have no idea what a wallet is or how to navigate it.
Saving for the kids is a fine goal if you stay on top of the investment and pull out if it gets to swingy. If you plan to sit on it till they mature and not do any trading, then I think there may be issues.
I don't think that there is an issue in keeping the funds ideal in cold storage. However, one must inform and explain about Bitcoin to his family members to avoid the incidents like you mentioned above.
I have maintained a cold storage for my Bitcoins and I keep explaining about Bitcoin to my friends and family members so that in case of any unfortunate incident they will be able to extract and cash out my Bitcoin holdings.