Indeed, rice is filling and cost-effective. Home cooks know this, and so do professional chefs - which is why, when folks order a burrito at a Mexican restaurant, there's a good chance it's stuffed mostly with rice. Many restaurants do this because rice is simply cheaper than other, even more desirable ingredients. In fact, the fast-casual burrito chain Chipotle has caught major backlash for this very practice.
When are your kids done with eating off the kids menu? Like most things, it depends on a number of factors, like the size of their appetite, their pickiness, and the cost of the menu items. But sooner or later, your little angel is going to be ordering an entree that costs double-digits instead of the kids' mac and cheese that comes with a fruit cup and a lemonade for $8.