If it was me, I'd probably just shake the bees out in the apiary and if the other hive lets them in, then great, and if not, then that's fine too. If for some reason you don't want the bees in the other colony, like if you are concerned about disease still, then I'd just put the frames with the bees in the freezer. That seems more humane to me.
Just personally, I don't requeen based on the queen's age alone. I understand why sideliners and commercial guys do that, but as a hobbyist, I don't think it's a big issue. I let the bees or the circumstances dictate queen replacement. If the bees decide to supersede her, I let them, and if she starts having some sort of obvious problem like drone laying or something, then I'll remove her, give them some eggs, and let them do the rest.