Need help with building a landing gear

HI guys. Basically I want to build a landing gear. However I need the landing gear to go down in one button press with one part moving after the other, and i need it to do the same again in reverse. Obviously with a small time delay between each movement

So basically, button press, object A goes to open and then object B goes to open
Press same button again, object B goes to close then object A goes to close