How can I recover some quality in this pictures??? Please help me! it's kind of important for my family...

It is hard to know what direction you are looking for this photo to take. It would be substantially easier if it was of higher quality. In the first instance I was not sure if the blue cast was intended by design or not, so have provided two versions.

a) to reduce the pixelation I copied the base layer and gaussian blurred it followed by erasure of the main details from the blur layer
b) I adjusted the levels and brightness and contrast
c) Hue and Saturation (colourize)
d) Overlaid a very low opacity orange layer for better tonal range
e) Desaturated background and top and edges of hair, eyes and teeth
f) Dodge & Burn layer to bring out eyes more and even hair
g) Recolour of entire photo to blue tones (if blue was the preference)