Initial ideas for my film opening!

Me and Clara have talked briefly about our film-opening, and together we have formed an idea of a western-themed supermarket extravaganza. 
To elaborate there would be 2 people in a supermarket. (Possibly a mother and son, possibly 2 friends) The child, or 1 of the 2 people would be miming shooting people and possibly lassoing things. There would be western music and non-diegetic lasso and/or gun sounds. The wannabe-cowboy would be so very entranced by their own imaginations that their cowboy antics would be contrasted strongly with their friend/mother grabbing their attention by talking to them. At this point the music would stop and all sound would be replaced with mundane diegetic sound. To begin with, the audience would not know that the rouge wannabe-cowboy was with anyone, however the second character would be introduced naturally when they find their friend/child. Our opening would end with the 2 people meeting.