Personally, Yao Ling wanted to ask about Han Xiang's real characters --- whether she was worth to be saved or they should only ruin the wedding for them. However, seeing the two biased people in front of her, she wouldn't be able to ask the questions without ruining the atmosphere so she didn't dare to ask that question.
That's why she let them choose between themselves what they wanted to ask about. More or less, they would ask the same question so she didn't feel worried for one bit.
After knowing what to ask, they called one of the servants to call the old man out. It didn't take long for him to come out. The old man sat down leisurely and asked, "Have you decided yet?" The old man was quite confident with himself. Who dared to refuse such a good bargain to obtain secret information? In his eyes, no one would be able to resist.
"We'll do it," Yao Ying answered.