The two others kids are strangely quiet and calm, which is in no way a bad thing in Eren's state of mind. Instead, he can actually smile at them a bit and offer to give them some speed on the swings. Which is exactly what he does and the two seem to be enjoying it.

Eren, on the other hand, is staring off and waiting for Mikasa to return. He is rather worried about her health now. Maybe he should have made her go sit on a bench instead off run after a rascal...