Also, the real plot hole in Children of Time is the way they erased the civilization from the planet. They never actually had a choice, because if they were interracting with the descendants, then they already did go back in time and create the civilization.
Look at the sequence of events. They meet an older Odo, he sabotages the ship and prevents them from going back, that Odo was never created, so he didn't sabotage the ship, so they hit the barrier and went back in time...
Star Trek XI had the same plot-hole. If Nero went back in time and blew up Vulcan, then by his time there was no Vulcan to go back and blow up. So he never went back. So he never destroyed Vulcan. So there was something to blow up. So he went back and blew it up. Its a paradox that keeps negating itself.
That's not at all the same as what happened in Trek IV, where they went back in time to bring a solution to the future, not prevent the problem from ever existing. You can alter history with time travel but you can't remove your original reason for travelling back.