If only NRL actually had the power to lead clubs in major game wide marketing strategies such as this!
The plus of having every club play at large central venues, makes it a lot easier to roll out competition wide promotions like this. If the NRL tried to roll it out, the messaging would be like
'Kids in free except at Pointsbet Stadium, 4 Pines Stadium and Kayo Stadium and potentially not at Belmore Oval, Leichhardt Oval, Campbelltown Stadium Stadium & Penrith Stadium'
Anyway, whilst I'd love for more to make cheaper for kids to go to matches, a bigger lever mover (in my opinion) would be if the game actually did proper variable pricing. As it currently stands, most clubs charge higher prices for their bigger/more popular games, but few do any proper reductions for their 'dud' matches.
If they are worried about their members reactions, allow the members to bring someone along for nothing / cheap.