Good call with Keldorn, Bex. But I will say that with Keldorn in the party, you're almost guaranteed to get (and therefore complete) Keldorn's quest within 3 days of recruiting him, and therefore you're hardly likely to be in Chapter 6 when he decides to go to the circus. Still, what if you need to re-recruit him afterwards? (Can this even be done? I've never tried it.) I say it's high time Keldorn and family returned to the Firecam Estate to enjoy some quality time around the dinner table, or playing in the front yard.
[ADD:] In the event that Keldorn is not recruited at all until Chapter 6, that will be because he is needed to replace some other party member who got chunked in Chapters 4-5, and therefore will be kept in the party and never truly reunite with his family at all. Still, we must consider those who do his quest merely for the EXP and/or to see him back with his family, and some of those people might wait until Chapter 6. In that event, they can simply go on a picnic (vanish from the game entirely for 24 hours), reappearing back at home the next day. [/ADD]
I've never understood Mrs. Harrold either: She vanishes at nightfall, leaving her husband to complain bitterly, and then reappears at the crack of dawn, and Mr. Harrold apparently has no memory of being bereft. This is evidently jetsam of some forgotten quest, but as it's the only remaining fragment, it's not even fit for Unfinished Business.
Don't worry, jester, I'm not suggesting that you (or even Sim) write up a huge "What If" mod, I'm just spewing forth ideas; they come pretty much of their own volition, and this is as good a place to scribble them down as any. Happily, the "missed opportunity" part is self-contained: Just find the Commoner dialogs that mention the PC's party saving the circus, and alter them so that it was some other party (with 7 members, so the PC knows it couldn't have been him) that led the heroic rescue. Later on, if anybody wants to tack on an actual encounter with this other adventuring party, the stage is already set.
Galactygon, having Aerie judge willingness to change teams based on party composition is a good idea, but hardly applicable: You can't tell what anyone's alignment is until after they join the party, and the purists say not even then: You have to talk with them, get to know them, and base your opinion on that. So Aerie should only be able to consider the Charisma and conversation responses of whoever does the talking, and also whether you have a Drow in the party.
Did you ever see the end movie of BG1? There are literally thousands of Bhaalspawn in the Realms. I agree that there's no need to have this hypothetical party led by one, but not that there are too many of them in the game already. An encounter with one could even avoid the "Oh, not another Bhaalspawn" factor simply by being discreet about it: No mention of divine heritage or the word Bhaalspawn at all, but in the event of combat, they might use one or more of the Ascension abilities (such as Hand of Murder) and that would be it.