Get some pieces of a lightweight material like balsa wood or cardboard. Make a 3-d figure of some creature like a rhinoceros, pig, dragon, or something that the child has never seen and will not see in his/her environment. Add some element which makes it unordinary to you, like clothes, wings, or an unuasual color pattern.
As you make the figure, instruct it to protect the child, and hang it from a string, intertwined with your own hair, over the child's crib. Ensure that its position there is stable.
For the child, it becomes a thing of wonder, fantasy, and *magic.* The creature has no identity which the child can associate with any role other than that of protector, and thus your sorcery is uncontaminated. In addition, the child can look up to the creature's image and wonder just what the heck that strange thing is, diverting it from other concerns and offering entertainment as it twirls
For the parents, the improbability of wings, clothes, colours, etc... serves to separate the servitor from normal animal representations, thus ensuring that they identify it by its role as a special protector. The use of a theriomorph for the image allows the parents to consider it as a living creature more easily than, say, a geometric arreangement or a solomonic-type sigil. Also, it looks less suspicious to others who may balk at the idea
of having strange symbols over the child, but warm to the presence of a cute little winged pig hanging over the crib of the little one.