How formal are the tux that the groom and groomsmen wearing? Are they wearing "tails"? What is the father of the bride wearing? How large is the wedding party? Will your husband be standing on the dais with the groom and groomsmen? Is the bride using a wedding consultant? Will there be a receiving line at the reception? If so, will you and your husband be in the line? Is someone paying several hundreds of dollars to a professional photographer to record the wedding? How much is the rental of the tux? More than 2 tanks of gasoline? Could your rental of the tux be your wedding gift to the couple if it is that important to them? I feel that perhaps you don't have enough information about this wedding. We have had 3 traditional weddings conducted in churches for our 5 children. We were the grooms family for 2 of them and our expenses included providing for the rehearsal dinner, the complete cost of tux rental for ALL tuxes
(however, all groomsmen were our sons), our share of photographer's cost. The bride's family paid for all bridal and bridesmaid's expenses plus the flowers, reception, dinner, dance, cake and limo. Much cheaper to be the groom's parents!