I have done it both ways with my kiddos.
In the younger years (usually up until 4th grade for sure), I just pick the books for the kiddos and plan out the pacing. As they get older, sometimes I let them choose from among several of my choices. At other times, if they have a burning desire to read a certain book, I'll put it in at their request.
Even as they get older though, I often will select several more difficult/classic titles that I really want to discuss with my kiddos and use those for DITHR. However, I wait to do this, until my kiddos are strong readers and also really love reading, because very difficult books can sometimes kill the love for reading (as those types of books take some time to get into)! The wonderful news is that you can make DITHR grow and change with you as your needs change!