Harry knew that they would be there for him. He didn't want to have to call in anyone else to join the fight, wanted to be able to solve this on his own and keep everyone safe, but a part of him - the part that had started listening to Ron, mostly - knew that they would likely need reinforcements at some point. That didn't have to be the Weasleys, though. He didn't just want them out of the line of fire for selfish reasons; even more than him, he thought Ron was going to need his family around and unharmed when this was all over.
He smiled at her and met her eyes, taking her hand in both of his. "I know," he said. "Thanks for believing in me, Ginny. Even if it's confusing for you."
He didn't blame her for being confused. He knew it wasn't her fault. It was Voldemort's.