Main equipment list - packing for the big event

Swim
Wetsuit
Swim goggles x2
Vaseline / glide on
Swim Hat (one will be provided for race)
Tri suit
Watch

Bike
Tri bike
Aero Helmet
Socks (pre-powdered)
Bike shoes
Chamois cream
Gloves
SunGlasses
Food box for top tube
Aero bottle
Water bottle
Cycle computer and mount
Cycle jersey / shorts (optional)
Repair kit and tools (see below)
Race belt

Repair kit and tools
2 spare tubes
Tyre repair kit (mini)
Mini multi toolset
Tyre levers
Mini pump
Gas pump
2 gas cartridges (full)
Chain-link
Plaster(s)

Run
Running hat
Trainers
Running vest / shorts (optional)
Socks (pre-powdered)
'Daddy bracelet'

Nutrition
4x Cliff Bars (peanut butter / oats)
3x Powershots
2x Electrolyte powder / sports drink
2x Powerbar gels
Marmite / Peanut butter to make sandwiches for special-needs bag
[the rest will be picked up during the race]

Recovery
Protein shake and bars
Freeze spray / Deep heat
Body soak
After sun

Essentials
Passport
Money
Phone and charger
Travel plug
Race instructions
Hotel details
Plane e-ticket confirmation (flight home)

I am sure there is loads more to add but hopefully this is a decent enough first draft.

Better get packing!