I'm actually really surprised at some of the replies. It's not a case of Mumsnetters being militant. Nobody is judging, or wanting OP to get into trouble. The OP asked us if it is fraudulent. Some of us are just answering them honestly that, yes, it is. We're not doing it to be mean, we're simply answering the question honestly.
It's the rules that you have to supply the address of the child's main residence at the time of the application. If you don't, it's a fraudulent application. It's not unusual for people to own a property but live elsewhere. The 'elsewhere' is the address which should be supplied, as that's where they live as opposed to simply a property you own. In cases of split parents, they ask you to provide the address which is their main residence. In this case, at the time of the application it was the house OP and their children currently live in, not the Dad's home.
For those of you saying it's not a problem as he will live there soon, I'm sure you'd be the first to complain if your child missed out on a place at your first choice school because someone else filled out the form fraudulently. As I said to the OP, this is the crux of the matter. If it's not oversubscribed, what she did was wrong but she'll probably get away with it as no major harm done. If someone else has missed out on a place though because of the inaccurate information she supplied on the form, that is wrong.
Imagine if we all had the attitude of "it's ok, you're just planning ahead doing what is right for your child" when planning a move while applying for a school place? People who live closer at the time of applying could miss out on their rightful places. This can and does sadly happen. If it's found out, you risk losing the place because it is against the rules and therefore it is fraudulent.