Thanks for your patience. I have consulted about this one and we have a recommendation.
It is noted that this is an unusual situation. Formats 2.12.1 says "The first item listed in the table of contents is generally considered the first page of the main body of the book." GENERALLY. The recommendation is that the acknowlegements should follow print order and come before the contents as in print. However, use p-page numbers for the acknowledgements and the contents and start regular Arabic braille page numbers with the next text item in the contents. In other words, GENERALLY the first item in contents is given the first regular braile page number, but not in this case because of the unusual print order.