Here's my question - Should I even mention this to ExH? My guess is like the last time, he will say some BS again to justify his behavior. I was so mad that I wanted to just call him up and ask him if he had drank too much. "Did you know that our son cried because he couldn't wake you up??"
But on second thought I don't know what it would accomplish.
I told S10 that next time I will send you guys to dad's only when one of you has a phone just in case you need to call me.
It's not worth it to fight about right now. I think making sure the oldest or the second oldest has a phone is really important. I'd also be careful about sending just the 8 yo. If that were ever a thing make sure he has snacks packed w/him just in case and if you can send a phone with him do so. However, if I were in your position I'd do everything in my power to make sure that the 8 yo doesn't go on his own.
Write all of this down. Dates, times, direct quotes from the kids. I know you're out of the States but child welfare matters in most places. If this keeps happening have a discussion with your lawyer before you have a discussion with exH. Find out what it may mean to have to fight for full custody and placement and what the qualifiers are on a parent being considered unfit enough for that to happen where you are. In the States it has to be pretty obvious AODA issues and/or mental health issues, long criminal history, or abuse (past or present and the future endangerment of the kids). I say all of this because picking the fight isn't worth it unless there are real tangible consequences. You can't really say "If this happens again I'm not brining the kids over ever again you can see them at my home where I can make sure they are safe," unless you have an actual way to back that up. And based on what I know about your exH is that he wouldn't go down without a fight. Knowing you can have a motion filed with a phone call gives you the real and tangible consequence that some one with AODA or untreated mental health issues needs.