Time to make her voice sound the cutest and most endearing, for her otouto's sake!
"You're asking two? Aahha! You don't even know how big they are, you silly brother~" she slightly mussed her hair affectionately. "I know you're growing, but there's only so much your little stomach can contain~"

Annnnd here we go!
"You two are here on your own?" the server had, from the expression, taken it all. Hook, line and sinker... "We have free kid sizes!"

That was soooo~ easy!!