I think that sounds more than fair, your 
consideration of others should be commended.  =)
I doubt anyone could even fault you for just
selling them outright since you didn't intend
to separate them and it has been so long (you said
some cels were sold as much as 5 years ago, I 
think it's safe to say that the two weren't
separated to make some extra money ^.-), but this
way you avoid ruffling the feathers of even the
people who just like to complain.  =)

Good luck in finding the matches!

Kim
aka Lady Zatara