VBA Engineer - you are correct in that the regulation restricts access after take off.
However to have access in the first place you still must satisfy one of the criteria that permit access (over and above being approved by the PIC).
Unfortunately the 12 year old daughter is still a security threat!
Regulation 4.67 Security of flight crew compartment — all aircraft
(4) A person must not be allowed to enter the cockpit after the aircraft has taken offunless:
(a) he or she is authorised to do so by the aircraft’s pilot in command or the aircraft’s operator and:
(i) is a member of the aircraft’s crew; or
(ii) is an employee of the aircraft’s operator; or
(iii) is authorised or required by the Civil Aviation Regulations 1988 or the Civil Aviation Safety Regulations 1998 to enter the cockpit; and
(b) he or she holds appropriate identification as a person referred to in paragraph (a).
(5) If subregulation (2), (3) or (4) is contravened, the operator of the aircraft concerned commits an offence.
Penalty: 200 penalty units.