Any decision that the court makes in relation to children is based on their best interests. The court won't impose a 50/50 shared care arrangement if you are going to live in another country, but the judge would have to be convinced that your planned move is in the best interests of the children and that contact with their father can be maintained in a positive way when you have moved. If you are the main carer for the children and have been to date, you have a good starting point.
Further, if the children are older than 10, then their views will be taken as an important factor. They will still be asked what they think by Cafcass if they are younger than 10, but their views become more persuasive the older they are.
If dad is resisting, you will definitely need to present a clear case that this will be good for the children.
All manner of evidence could be used - obviously the logistics are important, but also so are the welfare arguments.
You need to have researched schools, the local area, activities, opportunities for being outdoors - for example.
There's also the benefit of immersing a child in another culture, and the advantage of learning two (or possibly 3) languages.
You need to show how you will be supported in the move and plan for contact with the wider family in the UK if you have them here too.
I trust that this helps?
Can I clarify anything further for you?