First of all, you've put the letter in the wrong position... it is printed vertically and you need to rotate it 90 angle clockwise.
I'm not going to translate it all, but summarise as follows:
It seems to be a letter printed for the people who attended the couple's golden wedding party. They expressed gratitude for the attendance, and saying they're sending the Japanese tea cups (handmade by themselves) as the gift to commemorate the occasion. (This "letter" was attached to the cups they're sending.)
Their golden wedding was on 18th April 1987, and this letter was written in autumn 1987.