Just order a smaller size to start with to see how you and your pets like it. If it goes well, then order the larger sizes for a little better economy.
Good luck, and if you decide to try it, let me know how it works out.
I have a 3 year old healthy cat and also an elderly cat with an abdominal mass that may be cancer. (I had the aspirate done and it didn't conclude anything and I didn't want to go with exploratory surgery at his age) Do you think it is safe for him? He's not eating as well as I would like and has a sensitive stomach, but right now I am supplementing with canned Science Diet a/d and w/d as well as lots of vitamins.