Trying to take toddler photos ground level...ever tried KNEELING before them instead?
Below is some example pics of an adult sim kneeling in front of his toddler daughter. As you can see, from the result pics on the wall, you can get them pretty close to floor level when taking a photo of them in this position. I simply chose "take photo" option from the dad's camera in his inventory while in the kneeling position. Just try it out. (requires snowy escape or a kneeling or even better a sitting on floor mod)
Note: it CANNOT be a pose. It has to be a command from the menu given to the chosen sim.