OK, I'm sorry that this has happened. You need to see your lawyer right away, if you don't have one then find one quick. You can address this in court yourself, but it has to be done right the first time. When you're calling lawyers, even if they can't represent you in court then ask if their office can help you get the paperwork done quickly.
You can bring a motion to court asking for an order that the children be returned to Alberta. While you can't stop her from leaving the relationship or the home, you can stop her from taking the children out of the province or community where they normally live. I assume that your home is the home the children normally live in, at least for 3 or 6 months.
So there is something you can do. But you have to act quickly, and it has to be done right. This is going to be done on an urgent or emergency basis. I hope you have an address for her for service of documents. If not, you'll need to make some calls and try to find out. Also, call her and try to talk about this. You want her to bring the children back to Alberta voluntarily of course, but prepare for court. Remind her that she doesn't have the right to relocate the children out of the province without a court order, but don't get into a big fight about it if possible.
Does that make sense? Please reply if there's more to discuss about this topic. If I've answered you then I'd appreciate a positive service rating please.