Chair, I hope this is helpful.
You are not under any obligation to bring the witnesses back at subsequent meetings. You may schedule meetings at your discretion. I think many chairs under these circumstances would schedule a meeting of committee business. They might schedule a meeting of the subcommittee on agenda and procedure. You are not under any obligation to schedule clause-by-clause on Bill C-20 and bring witnesses when you expect the discussion to be on another matter.
Out of respect for the witnesses, and also fully in keeping with the rules—I don't need an answer now, but you can consult with the clerk—I think you would be fully within your rights as chair to schedule something else, or to convene the subcommittee on agenda and procedure, or to take other such matters that would potentially focus the discussion where it seems to be going anyway.
I just provide that as hopefully helpful advice, and hopefully it's received in the spirit of that. I don't need a response now. You can certainly consult with the clerk. We'll see in the notice of the next meeting what you decide to do.