Play it if: you're in the mood for two hours inside the head of a resourceful, self-aware infant, concocting and enacting daring plots to get what you want.
Don't play it if: you want something more narratively substantial, or you have a hair-trigger pet-peeve for anything to do with kids.
I've had a running idea in my head about a work of IF based around a robot protagonist who wakes up in a state of semi-assembly, and has to work to complete itself while having to work around its inability to carry out certain very basic tasks. I mention this because Child's Play is basically a complete fleshing-out of that idea, with the difference being that the half-formed PC is a human rather than a robot.
The challenge and fascination of the game is that the PC's goals are entirely straightforward and achievable for most human beings (i.e. retrieving a toy and playing with it), but require significant effort and lateral thinking for the PC here. The puzzles are surprisingly tough and complex given the limited range of actions the PC can take, but that sort of demonstrates the ingenuity of the game: it's all about milking your few reliable skills for as much as they're worth, and manipulating others to do the things outside your own capabilities. Even though they draw on the same basic principles, the puzzles never feel repetitive or boring, though I suspect that with this game Granade may have exhausted most of IF's potential for games based around plausible baby-behavior.
Plausible baby-behavior is another notable thing. The writing of the parents and the babies betrays significant personal experience with both. The children are believable in their free-form, goal-oriented behavior - most of the time, just living in the moment according to what their personalities dictate, and occasionally acting in the service of some higher agenda - and even more so in their elicitation of parental responses.
The PC is a touch more self-aware and wise than one might expect an eleven-year-old to be, but it was clearly intentional and it adds a neat humorous dimension to the story (with the PC taking pride in his/her age and refusing to commit certain acts as being "unseemly" for such an age category). As with other good examples of prominently-featured narrative voices such as Lost Pig, For a Change, and Counterfeit Monkey, the novelty doesn't outstay its welcome but takes a step back and lets the exploration and challenge of the game take center stage.
This is normally where I would butt in with some discussion of the less positive aspects of the work. But the truth is that I can't see any holes in Child's Play. The author's commentary might have worked better as a running part of the description rather than requiring a separate command for each note, but it would be absurd to count that as a flaw. The game is simply a good, fruitful concept fully fleshed out and executed with wit and polish. This is the kind of short game I think most IF writers want to publish at least once in their lives, and Granade should be very proud of it. Highly recommended.