Halflings are Small. Apply the Small adjustments and effects from Combat Scaling, including its ability, attack, AC, maneuver, Stealth, reach, movement, weapon-damage, ration, weight, and space rules.
Racial bonuses from these traits do not stack with one another; use the highest bonus to a given check under the bonus stacking rules. Thus, the racial Stealth bonus remains +2; fear saves receive the +1 bonus from Halfling Luck. The distinct +4 Size bonus to Stealth stacks with the +2 Racial bonus.