Your mother & family probably aren't capable of securely owning their private key either, so they can and should allow trusted 3rd parties like exchanges manage their funds. Leave it to these entities to also take the complexity out on the user's end.

If that's a problem, then I really don't think gas is particularly complicated. You have to put enough gas in your car to make a trip, and that's universally accepted as a simple fact. It's pretty much the same with Ethereum, except there's a competitive market for gas prices.

Again, a user that doesn't understand the very basics of blockchain / smart contracts / simple public-key cryptography, and things like gas really should not be part of this ecosystem right now. Crypto is in alpha-stage, and it gets significantly more complicated that these fundamental building blocks. It's actually been abstracted extremely well so that all the people that are in crypto today can actually use it.