A child safety seat assembly comprises a base, two connector arms assembled with the base, at least one latch assembled with the base and operable to lock the connector arms in position with the base, and at least a release actuator disposed between the connector arms and operatively connected with the latch. The connector arms are provided with locking fasteners operable to engage with an anchorage bracket in a vehicle to lock the base in place, the connector arms being movable relative to the base to adjust a length of extension of the connector arms outside the base. The release actuator is operable to drive an unlocking displacement of the latch to allow adjustment of the connector arms relative to the base.