"Exactly!" Luke grinned widely, and then rubbed his chin in thought. "Why if we didn't balance each other, it might... implode or something! And we wouldn't want that to happen." He winked.
Of course, if he had known his opinion was so important to her, he would have been flattered and surprised. He knew most people just saw him as a fun guy to be around, and even though he could be quite easy-going -except in cases where a certain Slytherin was concerned- he knew that most people also didn't give him a second thought that he could have important opinions or would be up for a debate, to play opposite to whoever. But knowing that his words actually held some leverage? That would have been eye-opening to say the least.
He nodded at her, smiling encouragingly. "Well, I doubt I could be as great a Quidditch player as he was," he grinned. "But I'll try my best." Of course, Luke also would try his best to get into the Auror program later but since Quidditch was a natural talent and not dependent on grades, he thought he'd give it a shot before applying.
When she told him about joining a summer youth orchestra, Luke brightened noticeably. "That's bloody wonderful!" he exclaimed, pulling her hands into his and starting to swing her around, twirling her under his arm. "And being in boot camp, you can't really see me anyways! But you can send me recordings or pictures." He seemed to be excited enough for both of them, but he couldn't help that. He was Luke Spencer after all.