We did KTTK last Sept with DH in a manual wheelchair. (brought from home) You should let them know ahead of time that your party will include some using a wc. Our guide, Rae - who must be the greatest KTTK guide in the universe - was wonderful, and we even talked to her afterwards about whether or not there had been any modifications to then tour on account of our chair.
She said that there were no significant differences, other than things like leading the group to use the cut-ins on the sidewalks, etc, on places like Main Street, instead of just having the group step off the curb. She took DH and I on the elevator when we visited the Utilidors, and at CHH.
There were only 8 of us on the tour, and everyone was very considerate, making sure DH was in the front at points where we "gathered" to listen to what Rae had to say about this or that. No changes in rides, since DH is mobile and could leave the chair behind.
We complimented Rae on how easily the wheelchair was accomodated during the tour, and how it really appeared to be a non-issue. She said that she appreciates knowing about wheelchairs ahead of time, because it enables her to envision her tour in advance and anticipate things like stairs, curbs, etc. She also seemed interested in our feedback, and said that they always like to know how well - or not - they're dealing with accessibility issues.
All in all - having spent two
Disney vacations with the chair - we continue to be impressed with how well CMs throughout WDW appear to be trained in dealing with these things.
My only complaint continues to be DTD. None of the doors in the shops or restaurants at the Marketplace have automatic openings, which we found very surprising, considering how accessible everything else seems to be.