Your kids should understand the importance of brushing their teeth and doing it on their own. Give them a brushing timer so they can form a good practice on their own without you hovering and correcting constantly.
Above is the LED Night Light with Wash & Brush Timer, it has two-minute toothbrushing timer, and a 20 second handwashing timer and built in night-light with auto on/off (it goes on when the room is dark, off when light). When your kid presses the hand icon or the brush icon a green light flashes. As the wash/brush session nears its end, the light flashes faster and faster. When the session is over a red light flashes a few times and then the light goes off.