This is the way I see it: Philippe & Mathilde want their 4 children to be part of their active life, and gently introduce them to their public roles. They are not locked away from public view, but attend annual formal activities (National Day, Queen Elisabeth Competition, Christmas Concert) and more relaxed activities (Museum Night, Visiting a company, a procession, a folkloric event, sport games) more or less according to their own interests. It's rare that all 4 children attend a less formal occasion at once with their parents.
Then there's also the annual family photo shoot on location and the official photos.
So all in all we get to see the royal children often enough to remember they exist, that there's 4 of them, that they are fluent in several languages (never underestimate this in Belgium) and that they also wear jeans to school
The benefit for the children is that they understand their roles, their public image and yes, their duties... But at the same time they're protected by the presence of their family. It would be so easy to shoot pictures of the children at the school gate every day, yet this never happens. Often there's a message on social media about Elisabeth & Mathilde shopping somewhere, yet no picture ever accompanies the message.
I think Belgian court has certainly managed a very good balance on how much they introduce the children to public life.
When their children will be big enough to officially step in where Astrid or (god forbid) Laurent is needed now, they will be well at ease - much unlike Philippe in his day.