Help to become best dad in the world.

[Richard Burns]

There are many ways to approach this but as has been said above you want all the wiring in the bed to be 12V dc for safety.
As a start point this means having a power supply to provide the 12VDC. These are readily available and should be sized to about 20% above the expected load of the lights e.g. say a 40W power supply for 30W of lights. They will need free air around them.
Cable connections should be enclosed to prevent inadvertent contact or disconnection.
Plan for maintainability as far as possible. Pass cables through conduit or trunking or machined voids in wood so that they can be replaced if necessary.
It would probably be easiest to have a hollow section in the bed that
can hold the connections to switches and cable joints and then just run the wiring to the lights.
If you get a standard power supply it will have a barrel connector centre positive contact (2.1 or 2.5mm), so it might be easy to use CCTV power connectors which have screw terminals, or if you start with one of those and then change to lever action push wire connectors this is simple, but slightly larger in size. The 12V power supply connectors can also be bought as splitters to distribute to multiple lights.
Flashing or non flashing LEDs prewired for 12V are readily and cheaply available on ebay and can be mounted behind coloured discs of polycarbonate or acrylic or perhaps in coloured plastic balls set into the bed.
Toggle switches or push switches for panel mounting are readily available, screw terminals may be easier than solder or quick connect tags. Take note of how long the panel mount is depending on the mounting plate thickness.
Just some initial thoughts to get you going and a messy picture as well!

 

[Simon Quartly]

There are many ways to approach this but as has been said above you want all the wiring in the bed to be 12V dc for safety.
As a start point this means having a power supply to provide the 12VDC. These are readily available and should be sized to about 20% above the expected load of the lights e.g say a 40W power supply for 30W of lights. They will need free air around them.
Cable connections should be enclosed to prevent inadvertent contact or disconnection.
Plan for maintainability as far as possible. Pass cables through conduit or trunking or machined voids in wood so that hey can be replaced if necessary.
It would probably be easiest to have a hollow section in the bed that
can hold the connections to switches and cable joints and then just run the wiring to the lights.
If you get a standard power supply it will have a barrel connector centre positive contact (2.1 or 2.5mm), so it might be easy to use CCTV power connectors which have screw terminals, or if you start with one of those and then change to lever action push wire connectors this is simple, but slightly larger in size. The 12V power supply connectors can also be bought as splitters to distribute to multiple lights.
Flashing or non flashing LEDs prewired for 12V are readily and cheaply available on ebay and can be mounted behind coloured discs of polycarbonate or acrylic or perhaps in coloured plastic balls set into the bed.
Toggle switches or push switches for panel mounting are readily available, screw terminals may be easier than solder or quick connect tags. Take note of how long the panel mount is depending on the mounting plate thickness.
Just some initial thoughts to get you going and a messy picture as well!
View attachment 42694

Thank-you.. food for thought will have a look.