Retrieval (moving kids from DGHs into centralised Paediatric Intensive Care Units, or moving kids between intensive care units for more specialised services e.g.ECMO) is one of my areas of professional interest.
Moving an intensive care patient is a big undertaking especially when there are multiple modes of transport involved.
Typically a team consists of a doctor or highly trained nurse (Retrieval Nurse Practitioner). These people can intubate, put in specialised lines, prescribe drugs, decide to change drugs/treatment tack and make ventilation decisions. They will be accompanied by an experienced ITU nurse who has specialised training to work on the team. Between them the hcp will usually have a wealth of experience of critical care and the ability to troubleshoot any patient or equipment issues that may arise.
Most UK services have their own ambulances and ambulance technicians who bring complimentary skills to the table - setting up kit: ambulance restraints (special harness to keep children safe on the trolley in the event of an accident), setting up the monitor and most importantly for the team I work on they often spend time with the family - running through the process, telling them clearly (often with maps) where there child is going, what will happen, reinforcing that if any family members are travelling independently to the new hospital they shouldn't tail gate the ambulance for safety reasons. They don't deliver clinical information but families need practical info (parking, will they get accommodation) and our techs deliver it brilliantly freeing up the clinical team to stabilise and move the patient onto the transfer kit.
Flying requires modifications to kit for space and clinical reasons - smaller monitoring devices, more batteries (as not all planes/helicopters have a power source that can be used). If it is a long journey you need to calculate that you are carrying enough medical gases (oxygen/air) and drugs, extra blankets as it can be cold. You need to make sure you have provision for team rest breaks eg. You might take a third clinical person to facilitate this.
Logistically you need to calculate where you are flying from & to (london- Iceland-USA has been my experience) how you are going to get to the uk airport (usually easy), how you are going to get to&from the foreign airfield. This is often more complex and the lack of certainty e.g. Will they have medical gases you can use, will they have a power supply often results in even more redundancy being built into the transport plan (more oxygen/ more batteries!).
You need to make sure you know exactly where the patient is going to eg.my hospital has about 6 itus over two sites - transfer team needs to know which ITU on which site.
You need to make sure staff and patient (and parents if travelling with you) all have appropriate travel documentation and visas.
On a practical level during a long transfer you need to make sure staff have food/fluid, access to the loo and comfortable clothing - a cold helicopter is not the place to be wearing a flimsy nursing tunic!
Retrieval is very process driven with lots of checklists. Families often find it disorientating as we stand there checking off - patient labelled, ventilator attached, spare gas, monitor on, drugs attached, phones present, notes on trolley but it is really important. You don't want to be the doctor who left the notes in Manchester and brought the patient to London...
I hope this helps to answer some of the "how would they move him questions". In summary it is eminently possible, but it is a big faff and poses risks to the patient but also parents and staff. Travelling in a blue light ambulance carries considerably more risk than a standard car journey... as a result where possible most retrieval services will travel off blue lights if their patients clinical condition allows eg. Moving round london in rush hour - blue lights to get through traffic. Moving at 5am on a Sunday morning = no blue lights and generally driving on the correct side of the road!