You tell Moonflower that you are, and ask if she would like to join in.

Moonflower: "Yuh uh!"

Moonflower begins to carefully stack buckets of sand on top of each other, creating a tall pillar. Once it's done, she notices Windcaller's flustered stare.

Moonflower: "It's a tower!"

Windcaller: "Oh. I-I mean, of course...!"

Moonflower: "Heehee! Hey, Windcaller, do you got many friends?"

Windcaller: "Well... everypony knows everypony in Hoofington. That... has to count for something, right?"

Moonflower: "Maybe, but you still look super shy."

Windcaller: "Ah, well... I just... tend to keep to myself, that's all."

Moonflower: "Why? You look like you're havin' fun with us!"

Windcaller: "I suppose... Though, it can be... somewhat... overwhelming, at times."

You continue to build your sand castle together. As time passes, the clouds above thicken, darkening the sky, and making it increasingly difficult to tell the time of day.