Welcome to the forum.
The prewired LEDs state they have current limiting resistors which means you do not need to control the current and can connect them directly to the power supply without them burning out.
I think it might be a nice gift. But you may need to supply a few more bits so that your dad can make the assembly as soon as possible.
An obvious inclusion would be a means of causing the lights to flash.
Initially an indicator flasher springs to mind but the standard types may operate the LEDs whilst they are off as well, as they have simple circuitry, so it would be best to make sure you get an LED flasher unit (cheapest ready to use thing available).
Inclusion into light fitting on a car can be complex as they is often limited space and wiring potential.
Hope it works well.