"What do you say to the idea of our getting these crazy kids back together?"
"I think we should try to get these crazy kids together again. What do you say to that?"
Basically, "What say ..." is an idiom meaning, "What do you say to the idea that ..."
"What say we go to movies tonight?"
"What say I pick you up at 8?"
"What say you bring your sister and her boyfriend?"
Student or Learner