Do palate expanders make the face wider?

No: It will make the "u" shape of your upper jaw wider, but not change the appearance of your face.

Possibly: Depending on the amount of expansion needed, the action of a palatal expander can give the appearance of an increase of width of the middle face.

Yes, in a good way: Palate expanders, usually done in 11-25 yrs old, will modified the patient growth and guide the horizontal and vertical growth components. It usually will give a good esthetic result since it helps to correct crossbite, achieved correct intermolar distance and correct arch form, lower deep palatal vault and increase nasal cavity and result in better air volume during breathing.

It can: orthodontic treatment, as a whole, can make subtle improvements to the overall shape of your face. The operative word here is improvement. If you have a proper occlusion, your face will have a more balance and aesthetically pleasing look.