If you want high quality, grain free for a descent price I would go with Taste of the wild. Do not look for life stages (puppy, small breed, large breed, etc) as they do not have those

Cali said it all tho...depending on what they are on, you should slowly switch them over. Typically you can do this in a week or two, since they do not eat much throw in a couple kibbles of the new food with a majority of the old food and about 2 days later increase the new kibble and decrease the old kibble, then keep doing that until they are off the old and on the new