The objects will spawn in a set X,Y? If yes, you can create a Function - the same way you create a sprite, or anything else -, then go to you event sheet, include your functions, and call them at random. Like this:
Of course that you'll set what your function does. To call them randomly, just create an action with "Call Function ------ choose("funcX","funcY", "funcZ")", and it will pick one of them randomly.
To make it spawn a limited set of times, set a local variable that whanever the object is spawned, it has 1 added to its value, then put another condition on your function that says "X<5", by example.