I hope your meeting goes well. Please let us know.
Preparing for your meeting like you're going into battle is the best way, really. And I'm glad you are keeping it businesslike (as much as one can).
My ex flaked all the time on the kids until he really felt he was losing them and they just didn't care. Then he seemed to finally get it. And after 11 years (almost) - the kids have not met OW - their choice. They are old enough to decide. It took a lot of pressure off them when I backed off and let them make their own plans with their dad.