It is heartbreaking, but just make it a great fun day, and even if they don't grasp the idea of a birthday yet, they will remember have all these amazing moments. That's really all that matters

She will and may understand. My son was mute, and he now talks. He tells me things that he remembers from the quiet days. It is amazing to hear "His side" of the situations.

Mine mostly did. But it was too overwhelming for them. We had to spread out the festivities over several days so that each thing was low-key. We had only one or two visitors at a time. There was one present to open a day.