I just tell them, "Wait, I can't understand and you need to take turns." This includes to my husband as well. Then I name one to go first and make sure I interject at some point if they go on too long and say something like, "let's let (insert name here) talk for a while and then we'll get back to that because it's very important but (insert name here) really needs to tell us something." This works, of course, only in an ideal world, but it's a way I try to handle it. I always give my husband the floor first because he's doesn't get to talk to me as much as the kids. Usually the toddlers don't have a long story to tell, so I let them talk before my 12 yr old who can go on for hours.
So, that's my response. After raising kids, we'll be great diplomats!:LOL