I think you have to be concerned with doing a lot more than that. Combining these procedures, particularly if being done under general anesthesia (as is likely in view of what you're having done) is associated with a risk of blood clots in the legs (referred to as Deep Vein Thrombosis, or DVT). If these break off and travel to the lungs it is called a pulmonary embolus, and the results, in that case, can be fatal or, if not, can cause significant morbidity.
You are right to be concerned about this but there are many things that can be done to minimize the risk. These include administering anticoagulants, such as heparin or Lovenox, the use of compression devices on the legs, early ambulation, adequate hydration, etc. It is reasonable for you to speak with your PS ahead of time to make sure these things are being done, as is likely. Together, they reduce the risk of this combination.
Elevating your legs may be part of helping swelling diminish - in the sense that you're "defying" gravity - but there are many more issues that need to be addressed in order to ease your recovery. And to maximize the safety of this procedure.
I hope that this helps and good luck,
Dr. E