Spending the $15 on some cushions and a cheap blanket makes for a much better game IMHO...hide the salami. 8)
I like most of your stuff Mike, but my back is telling me that ping pong on the floor is a fail. If cheap is the goal, and using the floor is the plan, then a lot less tape to outline a field plus 1 sheet of paper to make a triangle "football" would make for a fun and comfortable family game for ages 6 and up, as opposed to the family making game.
Cut some holes in the floor at each end of your ping pong table. Build the holes about 30 inches deep. Now the floor becomes a table.
Did you ever see guys with sewing machines sewing big tarps, truck covers and stuff? They stand in holes in the floor. Sewing machines are mounted to the floor and the floor becomes a big table.