Hi, when I used the G6 on my daughter, I would put a shot glass in the freezer for 5 mins before the sensor was due to be changed and then apply that to her skin in the seconds prior to inserting the new sensor. The coldness would in theory trick her brain into concentrating more on the feeling of the cold so when the sensor was inserted it didn't hurt as much.
Hope the numbing cream works though. Just another thing to try. It's not nice having to see your child be in discomfort like that.