D.F.
I thought I'd one more thing to the already good advice. I have 2 daughters and both of them did the same thing when they were that age. When they would grab my face, I would flick them just enough to cause a little pain and say 'no' calmly, but with a firm voice. And then I showed them, with a smile, how to gently stoke my face and said 'gentle' at the same time. The pain quickly deterred them from repeating the action and they soon learned to touch my face gently and in a loving way. As far as with other children, those children may not want to be touched at all. So I would just flick her hand and say 'no'(again just enough pain to deter her from repeating the action). This worked wonders for my girls. It may take a few times, but it will work.