ok so your using blueprint scripting thats what i use too. Your using something like a play sequence node to play the videos right. pretty much the switch on in is a node that has one input and multiple outputs and decides which output to use based on a integer you provide. but instead of providing a static number you want to plug in a random int in range node which will select a random number between 2 numbers you give it.
in the picture below youll see the basic way of setting it up. fyi i havent worked much with video stuff so the actual playing of video might not be right but selecting of which one to play is solid.
