I assume that your ex-husband still gets to see the children on a regular basis, if he lives nearby. If you move, would that still be possible, and if it's not, will that cause problems? That in itself isn't a reason not to go for it, but it's something to think about - instead of him seeing them every weekend, you might have to change to every holiday or whatever.
OTOH, if you're talking about working in NL when you're currently in the Ruhrgebeit or somewhere not that far from the Netherlands, then it wouldn't be such an issue anyway - there's no indication in your post, and that side of it will depend on whether you're currently in Belgium, Germany or somewhere close to NL or Italy or Spain or somewhere.
Regardless of all that, I think I'd go for it anyway - dealing with the children and ex-husband isn't an issue till you've actually been offered the job. Also, the children are getting to an age where they're more able to be self-sufficient - do you have friends who can help with things like taking them to and from after school activities or anything? See how far you get with the application, and remember that job interviews are two-way, that you're finding out whether they'd be as good as they look on paper, and if they'll provide the things important to you in a job. I think if it really is that great and you want to take it when offered, you'll find a way to make it work.
I've friends in Belgium - he's recently started a job in Germany, and is commuting weekly at the moment, coming back at the weekends. It's not easy, but it's better than unemployment. We've got offices all round Europe, and some people do work cross-border, or will make a regular trip once a week to one of the German offices when they're normally in Amsterdam (for example). I think a lot of it comes down to what it would if you're looking just in-country - the travel time. I think 3 hours each way once a week is okay, but every day wouldn't be, but everyone has different levels of what's acceptable to them. Working over a border might be a shorter journey than going to the next big city in the same country. Also, what is the nature of your job? I am usually based in the same office every day - other people spend a lot of time out on client sites, and are almost never back in the main office, and in that sort of role, it's expected you do a lot more travelling anyway. So there's all sorts of things like that to consider.
I'm sure other people will have more direct experience.