I can only imagine how your heart must be breaking right now, as you have had Lucky & Chance for quite some time now. But you are doing the right thing.
It's good that you will be able to see them in their new home.
When I adopted Katie from a foster home, the woman let me know clearly that she would be calling me for updates and that she would unexpectedly drop in to see how she was doing and asked me if I had a problem with that. I clearly let her know that I didn't. She did call me about 3-4 times and popped in twice and saw for herself how well Katie was doing in her new home. Maybe you can mention this to the woman and see how she reacts to it.

Wishing you all the best Lucky and Chance, in your new forever home.