This would worry me too OP. And I actually think having kids young, then getting a career started, can be one of the best models for women if the circumstances allow for it. Especially women who want to stay home with their kids for the most part, which I think is a very valid approach to childrearing.
The thing of course that is most worrying is that if she were to do this in the UK, she would have her family nearby to keep an eye on her or to support her, she would have the law to protect her, and society generally that would support her rights and those of the kids.
It is really different potentially in a place where those things aren't true. I also think that there is a real possibility she may find living in the ME is a real culture shock, and she may find it lonely, which will create it's own pressures on the relationship.
I do think you should have a talk with her OP, but I would first take the time to calm down, and also find out more about the laws and what things are like in the specific country she is intending to live in.
And I would not present it as a personal commentary about her boyfriend. But rather, a good % of marriages fail. In the UK, her interests would be protected, finanically (not as well as they ought to be, but there are protections) and in terms o the children. This is not the same in X place, in these specific ways. No one plans to get a divorce, but it is common enough to warrant some though. If that were to happen, if she could not leave with the kids, how would she support herself without family? Could she end up stuck? What rights would she have to see the kids at all?
Tell her you will always support her but being so far away, there will be real limits to what you can do.
Ask her to consider that once her kids are older, a career might still be difficult (if that is in fact the case, it may not be depending on where they would be.)
I also might suggest that before they marry, that she visit for a period of time that would allow her to see what life would be like there and meet his family - they are likely to be very involved in her life and she will depend on them in many ways.