Over time if ever
Handedness comes in at variable times in normal kids from mid 2nd yr to 4 or 5 if ever.Some kids will use both equally or favor one for one task & the other for another.A few will be ambidextorous.
There is no reason to discourage use of a particular hand at any age. Handedness is centrally wired. Strong preference one hand before 15 mo may be a sign of mild CP & should be evaluated.