Dear Pinbuster:
Because the association raised the additional funds, the association tournament directors -- perhaps with guidance from the board of directors -- should be entrusted with proper distribution of the monies into the prize funds.
Some of your "options" could be handled without any problems. However, your suggestion of additional "number of places being paid" is probably out of order (because your tournaments almost certainly have prize payout ratios incorporated into the rules). Of course, those ratios could be changed, but it would have to be done prior to printing of the official entry blanks.
You refer to four divisions -- Open, Women's, Open Senior and Women's Senior -- and some might object to a one-fourth distribution into each of the categories because female members would have the right to compete in all four tournaments while the male members could enter only two of them. But such a distribution wouldn't necessarily be improper, and the funds could be distributed in that manner.