Posting bail versus staying in jail should not have any effect on sentencing.  Your son might be acquitted and there wouldn't be any sentence.  If your son is convicted, the judge will look at the sentencing range/ guidelines, the facts of the case regarding the burglary, prior record, etc.  Your son has a right to bail and therefore posting bail should not have any effect on a future potential sentence unless while your son is out on bail, he commits other crimes or flees.