Hi I have a cattery, older cats are easier to be left at home because they sleep lots. The younger kitten though if it gets bored may try to play with the older one a bit more than the older one wants to be, also the younger one, if he/ she escapes out the door may go out for a run and be hard to get back inside, may go looking for you or may get chased by a dog etc.. When you go look at the catteries, ask what they feed the cats in their care, we supply the food that people feed at home so that there is less change for the cat. also make sure that they make sure all cats are vaccinated. If you do decide to put your cats in a cattery, make sure they are deflead and wormed before you put them in a cattery. Also go over them with a fine toothed comb like a flea comb to make sure their are no wounds from being in a fight before you put them in and when you bring them home. Take a blanket or one of ur jerseys that your cat has been sleeping on . Some catteries play music which can be good because that can stop them from focusing on other cats that may be swearing at them. ask to see a cattery before you book. Also make sure your cat has a secure cage for transporting to and from cattery in. There is so much more i could tell you but you will get bored. Cats are generally happy in catteries as long as they feel safe so lots of places they can sit and hide in is essential.