I would feel unjustified getting a full refund AND accepting the flowers. Since you do not want happy friday flowers the honest thing to do is refuse delivery imho. If it was me I would take the discount and enjoy the flowers.

For my brothers funeral the flowers were late AND they forgot the banner across the huge white carnation cross that I ordered and I got a discount on my next order, I did not get the money back, the arrangement was over 200 dollars.