Whether it's games, books, anime, or otherwise, Pokémon has generally been aimed at kids first and adults second, and Pokémon Sun and Moon is no different. While of course there are some references, jokes, and language that will go over their heads, in general children as young as 6 years old could make their way through Alola without much trouble.
The Interface Is Readable For Kids
As far as interfaces go, this is probably the best Pokémon title yet. The writing is large, colors are bright, indications are clear, and it's pretty easy to see what's going on and any time. There are even helpful reminders about what types of attacks are effective against other types of Pokémon.
This is an enormous improvement over predecessors as before, mastering different attack types required in depth memorization of increasingly large charts of all the different types of Pokémon to understand how to switch on the fly. So if you can't remember that Grass is Super Effective against Water, now the interface will remind you of that, so you don't make the mistake of putting your Litten out against Water types.
Mature Themes Are Largely Absent
The game is rated E, and while the ESRB sometimes has to make the hard decision about which side of the line to land on with ambiguously rated games, this is not one of those instances; the game is truly friendly for everyone. The cast of characters (both hero and villain) is diverse, and dressed appropriately, there isn't any foul language, and even some of the adult themes that you might see occasionally in a Pixar movie aren't present in Pokémon Sun and Moon.
Some of the language might go over kids heads depending on their age, but given context clues of conversations, it'll still be very clear what they need to do and what's expected given any situation. In general, the concept of "gotta catch 'em all" is fairly universal and doesn't require much explanation. While some of the puzzles that exist in Pokémon are intellectually challenging, this isn't something that kids usually struggle with.
Combat And Fighting Are Tastefully Done
Of course, like any Pokémon game, there is a lot of fighting. But like always, #Nintendo handles it well. There is no blood throughout the game, nor does it really show any types of real injury on the Pokémon who do get hurt. There are animations of Pokémon being knocked out that are tastefully done, and none of the fighting could be considered violent or visceral.
Overall, while one of the core mechanics of the game is you vs. an opponent (be it another trainer or a wild Pokémon), none of that ever becomes disturbing or graphic, and is as tastefully done as combat could be done in a video game.
The game is extremely kid friendly, and it's safe to say that Pokémon Sun and Moon can be enjoyed by virtually every member of the family. Make sure to grab different versions for each person so you can do trades and catch 'em all!