As far as I know, the proxy form only relates to voting at meetings. What Becks needs is a letter from his parents appointing him as their agent under section 121 of the Act. There is no need that I can see for a Power of Attorney (unless Section 121 only relates to receipt of documents, which I doubt). Worth a call to Fair Trading or a lawyer to get their view. This is what section 121 says:
121 Can an owner of a lot appoint an agent for dealings with the owners corporation?
(1) An owner of a lot may appoint an agent to receive notices and other documents under this Act if the owner is unable to deal with those notices because of intellectual impairment or physical impairment, illiteracy or an inability to read or write English sufficiently well or absence from the lot.
(2) A person must not be appointed as an agent unless the person is a resident of Australia.
(3) An appointment of an agent may be made at any time and may be revoked at any time.
(4) However, the appointment or revocation has no effect until communicated to the owners corporation and recorded in the strata roll.
(5) If an agent for an owner has been so appointed and the name and address for service of the agent is recorded on the strata roll, notices or other documents required to be given to the owner under this Act are to be given to the agent.