I would do two things: About one or two business days after making the request, I would send the schedulers a nice email letting them know that you are planning a route and need to know - one way or another - whether or not you are going to be assigned the shop.
At the point in time when you are actually re-arranging your schedule, simply delete the shop request. Schedulers fully understand that you cannot wait forever for an answer and that not assigning a shop to you right away means that you might find other options and become unavailable.