I would honestly try to steer clear of using cards for the first effect and try to do something more organic.
Earlier in my involvement with the craft, I would always perform card magic for people. It always felt like the most natural thing to do and it seemed to have universal appeal. After a while, I would always inevitably get the question, "So, do you do anything else besides cards?" After a while, I finally started to understand that I was offering people an unbalanced experience. I feel that if all you perform is card magic, people subconsciously feel you're not really a magician, but someone who just knows how to do really good card tricks. You're just a glorified Uncle Bob who knows how to handle a deck of cards. That's it. You become an actual magician once you diversify your repertoire and can perform miracles with anything. After reading books like Strong Magic and Absolute Magic, I saw that my assumptions had credible backing.
So with that, the first thing I would probably perform would be a leaf animation using a loop, followed by Leaf by Paul Harris. Or a simple Coin Assembly (Chink-a-Chink) with nearby pebbles on the sidewalk. I think doing something like that would feel a lot more impromptu and custom-made for the spontaneous encounter. Using a deck of cards for an opening effect just always felt mass-produced and cookie-cutter to me. The opening effect should have some relevance to the spectator or your current location to make it more inherently interesting.
Just some food for thought.
RS.
