Re: Jetstar's unaccompanied child issue it's state on their website (see below). To summarise if the child is not yet in secondary school (12 y.o for arguments sake) Jetstar will not accept them unaccompanied.
Virign will take unaccompanied children and cabin crew will supervise between the age of 5-11. 12 y.o is considered adult and they can travel unsupervised.
Re: Virgin's wheelchair/disabled policy, it seems Jetstar have a policy very similar policy without the media hoo-ha....
Children Requiring Supervision
Jetstar generally requires that passengers are able to travel independently. We do not have the systems, staff or facilities required to assume responsibility for assistance and supervision of passengers. Children requiring supervision will not be regarded as able to travel independently on the basis that they may cause a disruption or endanger themselves or others if travelling unaccompanied. As a guide, children who are not yet attending secondary school will be regarded as unable to travel independently and will not be eligible to travel unless they are accompanied by an appropriate Accompanying Passenger*. Jetstar may require proof that children are currently attending secondary school at check-in. Despite these guidelines, if a child is attending secondary school but their parent or guardian considers that the child is not sufficiently independent to travel unaccompanied using the service provided by Jetstar, they must notify Jetstar. Jetstar is not able to carry such passengers unaccompanied.
Limited Special Assistance
Generally Jetstar will not allow a person to travel without an Accompanying Passenger* unless the person can travel independently, meaning that they can travel safely without assistance, supervision or both. There are limited exceptions to this and you should contact the Jetstar Call Centre for further information. We do not have the systems, staff or facilities required to assume responsibility for such assistance and supervision. However, we do provide limited special assistance services to accommodate customers who need to travel with a guide dog, hearing or mobility dog, customers who require a wheelchair and customers who require two seats for themselves. If you need to use these special services you must contact Jetstar Reservations in Australia on 131 538 (+61-3-8341-4901) and in New Zealand on 0800 800 995. Those who have made special arrangements through Jetstar Reservations will be boarded first.