since the kids are young, most of them probably don't know the difference between the items in the meal, and a la carte - so they'd end up spending a lot extra, or having trouble paying if their card is restricted to meal, holding up the line. I think the advice is meant to speed them through the line without lot of putting things back at the register - less embarrassing for FARMS kids and kids whose parents restrict them. Having him try saying "ok, I'll buy that as an extra item." it might settle the whole thing. It's hard with shy kids because they never ask the follow up questions that might clear up the whole thing. Less shy kids probably navigated it right there and didn't have any issue to bring home.