New Guard Dog

We got a new farm dog 2 weeks ago. She is a Great Pyrenees/Golden Retriever mix. I thought she would be a good gentle guard dog for the kids. I have to do some obedience training with her though, she likes to wander. I have been walking her on a leash, which is a pain because the other 2 dogs can just hang out outside with out fear of them wandering away. Hopefully she will catch on soon. Serena - 3 years old