Yes, you can reply "No", bust as far as I know there is a way to ensure quest order. It just needs a little tweaking/debugging.
As far as Harny is concerned, I feel he's taken a lot of things upon his head to do, perhaps he should have a helper? What I'm trying to say is that having one NPC involved in 5 or more quests when there are a lot just lying around should probably be looked into.