Hi there! Your question reminded me of another thread floating around somewhere with ideas of things to do or say to characters. These might not all be exactly what you're looking for but maybe it will give you some ideas

And don't be afraid to do or say these things yourself, they love it when parents join in the fun! These are things people have done to get a reaction out of the fur characters or get the face characters talking. The one I thought would be really cute for your son at Crystal Palace would be to tell Pooh - "Where's the hunny? I have a rumbly in my tumbly."
Minnie & Mickey:
Ask Minnie if Mickey got her a wedding ring yet.
Minnie loves it when you wear a shirt with her on it! (So does Mickey

)
Wear a Minnie Mouse costume or shirt to Chef Mickey's (or bring a Minnie Mouse doll).
Ask Minnie how many dresses she has. Try to ask her in front of Mickey, or when a CM is around.
Tell Minnie she's the real princess.
Chip & Dale:
Ask Chip and Dale if they are squirrels (or gophers)
Call Chip...Dale and Dale...Chip....
Call Chip or Dale Alvin or Theodore
Ask Chip and Dale how to tell them apart.
Tell Chip and Dale you have nuts in your backpack.
Donald, Goofy, Pluto:
Ask Donald Duck where Mickey Mouse is.
Call Donald "Daffy" or wear a Daffy shirt around him.
If you have the talent, speak to Donald Duck in a duck's voice.
Wear your Pal Mickey or a Mickey shirt/hat around Donald
Call Goofy or Pluto "Snoopy"
Give dog biscuits/treats to Pluto
Scratch Pluto behind the ear
Tell Pluto he's a good dog.
Peter Pan, Wendy & Captain Hook:
Tell Captain Hook....TICK TOCK!!
Crow at Peter Pan.
Ask Peter Pan where he's from in front of Wendy.
Tell Hook he's a codfish.
Have a stuffed croc around Hook.
Where a kelly green shirt around Wendy.
Have on pirate paraphernalia around Peter Pan lol.
Cruella:
When you see Cruella.... BARK!!!!
Cruella gave extra negative attention in response to a hat that had a Disney feline on it! She also notices jewels!
Curella LOVES compliments!
Wear stripes around her.
Princesses:
The gist I've gotten is, they all LOVE to talk and have background stories, and they don't need much prompting.
Princesses oohh and awe over jewelry and clothing with images of them on it.
Ask Pocahontas how she says Hello.
Bow to a princess, and call them your highness ... they love that.
Speak French to Belle.
Ask Belle what her favorite book is.
Ask Snow White how the Dwarves are doing.
Ask Mulan if she's found her true love. When says no, tell her you'll put in a good word with the matchmaker.
Princesses LOVE little boys!
They also love hand drawn/colored pictures and CAN accept them!
Pooh & Friends:
Ask Eeyore if he's lost his tail.
To Pooh: "Where's the hunny? I have a rumbly in my tumbly"
Ask Tigger for bouncing lessons.
Alice & Wonderland cast:
Ask the Mad Hatter for his "autograph". He may draw a picture of a car and a graph.
Tell the Mad Hatter it's your Unbirthday.
Ask the white rabbit for the time.
Mention that you have a cat to Alice.
Dwarves:
Call one of the 7 Dwarfs by the wrong name, very funny, especially if all 7 are present.
Ask Dopey what 1 + 1 is.
Mary Poppins:
Say "Supercalafragilisticexpealidocious" to Mary Poppins.
Ask her to say it backwards.
Ask her how your kids "Measure Up!"
Toy Story:
To Buzz: Point behind him and yell "It's Zurg!!! Oh No!!!"
To Buzz: Ask him exactly where "Beyond" is.
To Woody: "There's a snake in your boot!!!"
To Woody: "Somebody's poisoned the water hole!!!"
General or other:
Give the villains a hug.
Wear a Universal shirt.
Have a stuffed Simba when you see Rafiki.
Offer Stitch a cookie.
Wear something with Stitch on it that he can take, like a backpack.
Stitch and Meeko are known to rummage through purses and backpacks for "food."
Ask Meeko if he is a badger.
Try calling Mushu a lizard.
Prince John - Tell him he's the rightful king, and he'll agree!
Sing Bear/Bare Necessities to Baloo.
Salute the green army man in MGM.
Wait in line to see Capt Jack, but when you get to the front act like you were in line to see Davy Jones.
After a picture op, tell a fur character they blinked or their eyes were closed lol.