Stir together first 5 ingredients; cover and chill 8 hours.
Soak wood chips in water at least 30 minutes.
Prepare charcoal fire in smoker; let burn 15 to 20 minutes.
Rinse chickens, and pat dry. Sprinkle each chicken with 1/2 teaspoon salt and 1/2 teaspoon pepper. Place 2 lemon halves into the cavity of each chicken.
Drain chips, and place on coals. Place water pan in smoker; add water to depth of fill line. Place chickens on lower food rack; cover with smoker lid.
Cook 1 hour and 30 minutes to 2 hours or until a meat thermometer inserted into thickest portion registers 180°. Serve chicken with sauce.