An Outside Accountant Does my Bookkeeping. Do They Need to Purchase QB Point of Sale Too?

No, your accountant does not need the sales details in QuickBooks Point of Sale - just the summary of the information that you post to your QuickBooks Accounting software.  Just transfer your summarized sales information from QuickBooks Point of Sale into your QuickBooks Accounting software.  Then, just as you've always done, send the QuickBooks Accounting software file to your accountant for review.