@jackg, @NeuroticFish, @PlagueDeath, as @OP said that of course his friend's parents are Boomers who in fact don't understand more deeply about the latest technology, I personally think that it's an unstable decision to separate wallets from assets that @OP wants to send to his friend's parents. So, IMO it would be better if these assets were stored in 1 Non-custodial wallet on the smartphone.
It's not an advise to use it, however, all in one could be Trust wallet. Still not online/web, even more, not even open source, still, it supports multiple coins (I don't know which) and afaik it's self-custody. Keep in mind that it's owned by Binance.
@NeuroticFish, @OmegaStarScream, I've done some research on TrustWallet, they support $BTC, $ETH and also $LTC, but not $XMR. So, if @OP wants to transfer his assets to TrustWallet, this can't be done. But for @OP, you can use
Atomic Wallet, Atomic Wallet is a secure wallet which, if I'm not mistaken, was developed by the Komodo project, they support all the assets you mentioned above. Hope my response can help you to solve your question.