You started off by saying
there are addresses for hotels etc but people’s homes don’t always have exact addresses more the areas
but then said
I mean they would be going to a capital city of the country and stay with his sister and family. It’s a well developed city
In. which case there is a proper address and it sounds like he is fudging so you are kept in the dark.
FWIW friend was married to a guy who came here as an asylum seeker and was on the middle of a divorce when exh said he would like to take the children (18-21year olds) to his home country.
Friend thought what could possibly happen as they were all adults.
Fortunately I had a friend from the same country who had her adult child detained in the airport on the way back because under the law of the country any child who has a parent from that country if they visit as an adult, even having a foreign passport they have to do the Military Service. It took a lot of money to get friends Ds back into the U.K.
Friend tackled her ex about this and it turns out he knew of the ruling. He was more concerned how she found out.
Just because you think someone isn’t like that you have to look at their actions and not their words.
Nothing from what you say is demonstrating that this guy will bring his children back.
It could all be fine but even if there is even the fraction of a percent that things might not be Then is it really worth playing with your children’s lives.