The cute graphics and characters are likely to appeal to younger children (especially girls), although they may struggle a bit with the large amount of reading involved (and the japanese words, which sometimes take us a while to figure out how to pronounce). The game is a classic story of good triumphing over evil, and as Chibiterasu needs the help of his friends to succeed, shows that teamwork is important. There's also plenty of opportunities to help people out, as there's always someone who's misplaced something, or had it stolen by the demons. Some children may find the relative open ended-ness a bit boring (I know my five year old cousin would, as she prefers more action-filled games), but others may find the story and exploring interesting. The combat and puzzles are quite simple, and they're unlikely to die a lot and get fed up, as any deaths simply result in them being respawned a bit behind where they were.
With no sex, swearing, or gore, Okamiden has little for parents to be concerned about. Seeing as you're playing as a dog, there is some minor violence, as you go around nipping at demons who don't bleed, and once defeated, simply collapse on the floor and fade away, leaving behind only some flowers, but it's really nothing too serious.