Yeah, but the reason they "seem" bigger, is because they have proportionately much smaller heads, while their eyes are the same size as adults (so the irises seem bigger, though they aren't actually. But because Yoda is already quite small, they had to exaggerate the iris size. In other words, this race either have shrinking irises as they age, or Grogu is a slightly different (sub)race than Yoda. Obviously overthinking this... but that's what we fan do!