1. Before release
Note: all arrows around balloon, both inside and out are normal to surface
Force of balloon surface on hand
Force of straw on baloon surface
Straw
Force of air on inside balloon surface
This is supposed to be a hand squeezing balloon shut
Note: force of balloon itself on air and air on the balloon are omitted.
Force of hand holding balloon closed
Force of air on outside balloon surface

2. After release
Force of straw rocket pushing on balloon
Reaction of exhaust on straw rocket
Straw
Exhaust action due to air inside balloon being forced out
Note: all arrows around outside of balloon are normal to surface
Force of outside air pushing on balloon
Note: force of balloon itself on air is omitted.