Also another option.
Create HUD like layer called SHOP. The layer is hidden by default.
When the player opens the shop.
Set timescale to 0 to pause the game.
Show layer "SHOP"
on close of shop
hide layer "SHOP"
There might be some trouble with it, but it saves effort in regards to enemy positions and states.... if you go with the prior poster. There is a plugin called Spritebank. Which I think will do what you want.