Orthodontia that Can Impede Speech Work:

Braces and palatal expanders can make it difficult for children to say palatal sounds

Consider the Duration of the Treatment:

Are the braces and expanders coming out soon or will they be there for a while?

Help Get Optimal Tongue Placement as Best as Possible:

Use mouth puppets or diagrams to show the child where the tongue should go for the different palatal sounds.  Work with the child on being able to describe the correct tongue placement and air flow for each sound (for ch, j, sh: sides of tongue resting against upper teeth, tongue tip down so it is not contacting the roof of the mouth, air flows down the middle of the tongue and out the front)

Have the child try to produce the sounds around the orthodontia as best as possible.  If it will be a while before the braces/expanders will be removed, try several different positions to get the best sounding productions and use those.  If the child will be out of the expander/braces soon, focus on optimal tongue placement so that the tongue will be in the correct position once they are removed.

Homework:

Have the family practice for short sessions, more frequently.  I typically recommend 5 minutes, twice per day.  Have them talk about the correct tongue placement and then work on getting the sounds as close as possible in isolation (sound by itself, not in words).  Once the child is very efficient at this, you can have them start practicing single words that contain the sounds.