Percy had been in the middle of casting a cleaning charm on Lucy's soil-dirtied hands when an object flew their way. He immediately switched his spell into one which grabbed hold of the ball and levitated it as he stood up, eyebrow raised as he looked for where it had come from. He saw the young woman and even younger boy (who looked to be within a year of Lucy's age, though Percy sometimes found it hard to judge children's ages on sight), and his lips quirked up in amusement.
"I believe this is yours, young man? Lucy, why don't you bring the boy his ball." He lowered it into his daughter's hands and encouraged her with a nod to bring it over to the boy. He always enjoyed an opportunity for her to meet children her own age who weren't cousins. Lucy looked like she was about to play shy at first, but then she grinned and ran over with the ball, offering it to the boy.