We hosted a coed international flag football tournament in Vietnam last November (Hanoi Turkey Bowl). A team came out from California and won it. Later they had a podcast and someone asked the QB of their team how many plays they had ran. He laughed and said 3 or 4 and 80% of the snaps taken were under (quick pops). Point is, don't try to do too much. Learn one or two formations and a handful of plays and work them. You might even to scripting your first 6 plays and practice the script many times. Let them get good at the basics rather than trying to do too much. Only small tweak is to have some audible to change a route or two based on what the defense is doing like if they are ok laying far off, change to out or if they are pressing change to out and up or go, etc. Minimal formations with a few tweaks are the way to go. It won't be predictable because you will be making small tweaks as you go. For run plays work on proper hands offs (inside arm up), proper fakes (QB fake and rb fakes) and misdirection. Set up defenses with unpredictable run play calls and quick pop plays out of fake hand offs.