Well "Fly", two wide-outs run straight down the sideline for a pass.
"Slants", two wide-outs run about 10 yards and then run an angle route towards the middle of the field.
"Flags", same as slants but cut towards the sidelines.
Basic running shit since it's just flag football and some trick plays such as:
"Hook and Lateral", wideout runs about 5 yards and quickly turns around and stops, catches the ball and laterals it back to a runner coming up behind him.
"Direct Snap" QB in shotgun with Halfback next to him. Instead of the center snapping it to the QB, have him snap to the Halfback.
"Flea Flicker", QB hands the ball to the HB and then drops back. Before getting to the line of scrimmage, the HB looks back and laterals it to the QB who bombs it to a wideout who ran a fly route.
Keep them to a minimum and simple since it's for fun.

Will there be linemen?