Welcome to YT!!
It doesn't sound like your little ones are crate trained, right? I wonder if instead of sleeping in the night, they get bored and as "something to do" ask you to take them outside. Mine always started out being crate trained, because it taught them that night time was for sleeping and that they could hold it until morning. If you don't want to crate train at their ages, how about limiting their area at night? To a bare-floor room or an x-pen etc? That might help re-train them that night time is free time. It may require a few nights of not responding to barking (better not start on a work night!). It would also limit the area that accidents could happen. That would be what I would try......
Let us know.....