Nintendogs + Cats is a virtual pet game that asks you to take care of one of a number of different breeds of cats and dogs. You can teach them tricks, take them for walks, enter them in competitions, and even teach them their name, using the console's built in microphone. Once done, all you need to do is say "Here Thor!" or whatever you've named your pet pooch, and your canine chum will come running (or at least, that's the idea).
Perfect for little ones who just want to play with a fluffy companion, there's not really all that much of a structure to Nintendogs. There are no goals, no real rules, and no objectives - it's basically a game about stroking a dog, taking it on walks, and finding new things to buy for it. That said, there is a little more to it, as you do have to keep your dog fed and watered - and doing so costs money. In order to get money, you have to enter your dog in various contests (agility contests, frizbee competition), and even coming last nets you enough cash to ensure your pooch won't go hungry for a fair few days.
It's important to note, too, that there's no need to come back to the game every single day to keep your virtual pet clean and fed. While on the DS version, your dog would run away for a while if you neglected it, Nintendogs + Cats (thankfully) ditches this, meaning if you leave the game for days, weeks, or months on end, your pooch (and cat) won't die of hunger - they'll just be even happier to see you! They also don't grow old, or die, which means there shouldn't be anything upsetting for kids.
While there's no voice acting in the game, there also isn't that much in the way of reading to do, and that there is is either sparse enough, or unimportant enough that you don't have to read to be able to play it. Entering competitions is perhaps the only point where those who can't read may struggle, but once a parent's shown them what to do, they'll be away.
As a pet simulator, Nintendogs + Cats is completely free of anything even slightly questionable. The dogs stay as puppies, so you don't have to worry about mating or death, and it's all generally very cute, cuddly, and nice.