I am sorry to hear about this concern.
I would not recommend cranberry at all. Great that you asked the question.
Cranberry is designed to somewhat help to acidify the urine. However, if there are already bladder stones present, it will be of zero benefit to help.
Not to mention, some bladder stones form in a more acidic environment like calcium oxalate, so giving cranberry actually could make the problem worse.
In addition, the stones will contribute to recurrent bladder infection, because the stone "surface" is nice for bacteria to get established on inside the bladder.
Now, there are a few diets that can actually "dissolve" certain types of stones, including struvite stones. One example is Royal Canin S/O or Science Diet C/D. I would absolutely talk to your vet to see if a stone dissolution diet might help.
Otherwise, I would not recommend the cranberry currently.
Hope that new information helps!