John, I have no clue how big you should build that deck. But you have painted a pretty picture of what you aspire to have in place for those beautiful summer evenings, spent with your lovely Wife, in your new home. You very obviously love the evenings outdoors, with this great and wonderful patio, you will be able to enjoy them, just like that picture you painted.
Something that I want you to keep in mind for your evenings spent, gazing at the stars and wondering.......go to a nursery and chose some flowers that are renowned for their evening fragrance. That will only enhance your experiences during these warm and beautiful summer nights. Along with all the other experiences of the night, you will enjoy aromatherapy too. You must listen to me, take that time or ask your Wife to take that time, to bring night flowers to your deck, you will never look back, nor will you not be glad that you heeded my advice. Find those fragrant flowers that bloom in the night.....most of them really enjoy the warm evenings of summertime. This should be as important a job as getting that patio of your dreams built......Oh those beautiful dog days of summer, coming on fast.
Good luck with advice on the dimensions of the deck. Picture that beautiful French door, opening to this deck, your barbeque, the night time enjoyment on this patio, in your new home. Have the best that this wonderful day can offer. Cindi