Too small dining room for special occasions....
Clean and paint the garage walls/floor, make curtains to cover open shelves. Put pictures on the wall, flower arrangement some place, or a floral wreath on a wall. Put up folding tables and chairs, cover with fabric tablecloths store bought or yard goods from fabric store. Drape something over air compressor, lawnmower, etc. or put folding table over these items with long tablecloth to hide them. (We do have a storage bldg. out back that holds many things usually found in a garage, which helps.)
I have a large family and the above was my solution to not having space to put up card tables or room at the dining table.
The chest type deep freezer serves as food or beverage serving space as well as a folding table. Usually I use the dining table for serving food buffet style and put drinks and desserts in the garage.
We use china and the works for special occasions and go less formal other times (we are not formal folks!)
Our family keeps increasing (about 24 now) and soon will need to raise the garage door and continue on out into the driveway!!LOL!! We do have a window air-conditioner in the window and ceiling fan. The storage area has louvered folding doors.
Sprucing up the garage makes a very nice dining room.