To the Bloodborne comment: Bloodborne is a game rated Mature made for players who want an over the top difficulty and that is all about the challenge. Therefore, a mode where you don't take damage is completely out of place.
Star Fox Zero will be a game rated E for Everyone and like Miyamoto stated, will probably be the first action game for some kids. Therefore, a mode where you don't take damage and can freely fly a flippin space ship while shooting lasers is not a bad idea at all.
Star Fox Zero, as almost all previews stated, will have a solid difficulty curve and will provide a decent challenge on his normal mode. As long as we have that, I don't see were's the problem of having a completely optional baby mode where the kid can freely imagine his/her space adventure without a game over screen popping out.
