Yep, that should do nicely, now as long as you can get a reference to the player controller or wherever youve put that, you can spawn new bubbles whenever you want.
you’re getting a random target between 0 and 150 - do you have 150 targets in your level? The random int should really be between 0 and the last index of the target array.
Also in your begin play, when you get all actors of class, i would save that array as a variable, to refer to later, rather than directly plugging that into the other functions. Just keeps things neater and you have a reference to your target list whenever you need it.
Thanks, that worked i only had 144 targets not 150 
Awesome glad you got it sorted and thanks variss for helping I had forgotten about doing it the way you mentioned