Here "blood" is a metonym that stands for a person's death. The phrase "be on us and our children" is an idiom that means they accept the responsibility of what is happening. Alternate translation: "Yes! We and our descendants will be responsible for executing him" (See: [[rc://en/ta/man/jit/figs-metonymy]] and [[rc://en/ta/man/jit/figs-idiom]])