The show, "Fantasmic" at MGM is essentially about good versus evil and features Disney "Heroes" and "Villains". As such the actual Black Cauldron plays a part in this story (not the other characters from the movie but the cauldron itself). There is a Villains Store at MGM as you go towards the Fantasmic show and at different times they have "ensemble" t-shirts, mugs, key chains etc that do have the cauldron itself on it.
I have never seen anything with Tron other than the video/dvd.
I did get to meet Bianca as a costumed character during the 25th celebration at WDW and she was featured with Bernard in the parade at that time but I haven't seen her since then. If you ask any cast member who is a character escort, they should be able to use their radio system to determine if there will be any appearances of them during your visit.
I went on my honeymoon to WDW in October. My husband was neutral on Disney before we went while I was the freak. But after experiencing the awesome shows, food, atmosphere he's very excited to fit in two more trips this year so, I'm sure you can help the Disney magic take hold of your new hubby.
Congratulations!
Brenda