Bro, if you keep your car clean the roaches will lose interest and find a new home.
Give the floor boards of your car a good vacuum. Wash all the mats with soap and sun-dry them thoroughly. Get some stain removers and remove any signs of spilled food or drink on the seats if they are fabric. If leather, get leather cleaner. Give the interior, i.e dashboard, door panels, centre console, rear arm rest, all seats and head rests a good clean with a damp cloth to remove dust and any bits of food and dirt.
I know your kid spills food once and again and you cannot stop that. Your best bet is to make sure you clean thoroughly when spills occur.
Insecticides, traps, pandan leaves, etc, etc are all but temporary measures that chase them into hiding. As soon as the strength clears with the air they'll come out again. Keeping your car clean will ensure they disappear for good.