"도와드릴까요?" has same meaning with "도와줄까요?"
드리다 is humble form of 주다 used for someone who is superior in status.
Can you help me?
나 좀 도와줄래? informal
좀 도와줄래요? formal
좀 도와줄 수 있어요? formal
좀 도와주시겠습니까? very formal
Can I help you?
도와줄까? informal
(좀) 도와줄까요? formal
도와드릴까요? formal
도와드려도 되겠습니까? very formal