Unfortunately, change of primary residence is very, very difficult to obtain, no matter whether you are the mother or father, and the term 'full custody' is no longer a term the court uses, nor does it often make orders to that effect. What that means is that even if, on the small chance, you were given primary residency, you would still probably be looking at a shared care arrangement of maybe 50/50.
The court is adherent to the 'best interests of the child' standard, so you would need to show a judge why having your kids move 100km away from their familiar lifestyle, friends, school and routine is better for them than staying with their dad. To uproot them from their lifestyle is not often considered in the best interests of the child, unless they have been exposed to a high level of family or domestic violence, drug use, criminal activity, neglect and the like, and it takes an extraordinary degree of evidence to make those kind of arguments. "My daughter is getting to that age" and "it's time I had them" isn't going to cut it.
If I'm court-cold honest, I would say you would be wasting your trying to get primary carership. I don't know what your involvement in the kids' lives has been so far, but if you have been an active parent and have a secure relationship with both kids, you would be better negotiating a week-about arrangement with the father or something else that suits.
I don't mean to dash hopes, but the courts don't buy into sympathy votes - they're realists and they don't sugar coat. You would be hard-pressed to argue that a change in primary residency is in their best interests on the reasons you have so far provided. Contact Legal Aid and book in to see a solicitor - they can give you free legal advice. I hope this helps.