go into "update fastpass+". select date, then "select new time" this will give a drop down for new times along with check marks next to each person of your group. Select the individuals that want another selection and change the time. Once they are on a different time schedule you can go back and change experience.
Nevermind. This is what I had to do on our previous trip.
Just went into change experience and it gives a individual selections once you pick a new attraction.