Stating the total number of volumes is an agency decision anyway and if the agency hasn't requested that, you don't have to do it. In this case, since it is not possible to know the total number of volumes, it can't be done anyway! Just leave out that line on the title page. See Formats 2.3.8.a(1).
As for print page numbering, each title page shows the print page numbers in that volume. If every page in every volume starts with 1, that's what it is. If appropriate, consider a transcriber's note on the transcriber's note page of the first volume that states the each braille volume begins with page 1 as printed.
You'll number the volumes themselves consecutively and that's about all you can do in this situation. The reader will have to use the table of contents to find out exactly what is in each volume. All you can show are the print page numbers that are there.