We are in a similar boat. My daughter is 14 (yes, also ADHD; but I have friends with teenagers who don't have it that are similar). My son is 7. It’s a vacation and I want her to be happy and we will do plenty that she wants to do and still use the schedule we have found works best for us.
It is also however, our first trip to Disney in 3 years and it will be shorter than our previous trips. I fully intend to exercise both the “stay in the room” option and the “wait for us at the end of the ride” option, whereas previously I had only used the latter. Once I put her in the gift shop when she didn’t want to ride Winnie the Pooh with us. We had missed it on our prior trip because of her and I just wasn’t going to miss it again. I didn’t ask a CM to watch her; but I told her to stay close to the counter. She ended up joining us in the line and riding. In the Mexico pavilion at Epcot she sat at the table and colored her Duffy while ds and I rode the 3 Caballeros ride.
She’s not generally contrary; but she can get in a state where she’s just done before my son and me and had enough of “being out”. For example, most people recommend a midday break in the summer. She’s pretty much let me know when we tried it on previous trips that once she gets back to the resort and gets relaxed it is really hard to get back out. In 2013, I ended up missing MSEP and Wishes after being at WDW for over a week because (going against advice) I saved it for the last night of the trip. We went to MK that morning and everyone knew the plan. Rope drop to noon, pool then rest and back for MSEP and Wishes. It had been the plan from the beginning of the trip and talked about several times that day. We had done the pool and gotten a nap and I noticed she was slow getting going. When I said “let’s get dressed,” it was then she told me she didn’t want to go back to the park. No amount of convincing would help, nor did reminding her it was our last day. She said go without her; but I wasn’t comfortable leaving her at 10. She apologized a couple of days after we got home and told me I probably should have just made her go; but I didn’t want her ruining the night with whining then reminding me she offered to stay in the room.
When we came back the following year, we adjusted our schedule so we either start early and end around 2 or we start around 2 if we want to stay into the night. We also do a version where we start at 10 and end at dinner time. We also did the night time entertainment at MK on day 3 of 7.
She also isn’t adventurous when it comes to rides. It worked to my advantage before because there was no complaining about not riding stuff ds wasn’t tall enough to ride. That also means there are a few things I have never done due to being the only adult. My son is flexible and somewhat adventurous and I would like for him to be able to enjoy a few rides he hasn’t been tall enough for previously…rides that she will likely still refuse to do. On top of being 14, now she has her own phone so I tend to give her and as a result, my son and myself more freedom in certain situations. I'll also be dividing our food funds onto 2 separate gift cards so she can carry her own.