6 year old doesn't like 10 week old kittens

Alright, My 6 year old cat is not taking a liking to my 3 kittens ( adopted the other 3) I knew he never like them because if he made it into the room he would strike the kitten if he/she got too close. Now my mom, just today, let them roam around the whole house and outside so they can get used to it. They are doing really well, they go inside than come back in. But my older cat hates them! Whenever I see the strike of the paw from my 6 year old I tap him on the head pretty hard with the palm of my hand. Because that's what he grew up with, when he bit us we struck him on the head so he got the message. But I've been doing that and now he is still trying to strike them when they just pass by...any opinions on what I should do?

Please don't hit your cat - that's really not a good way to discipline him and he's not being naughty. His reaction is perfectly understandeable. Most 6 years olds will get a bit fed up with boisterous kittens around the place. Look at it from his point of view - he used to have you and his house all to himself, then you bring in 3 kittens! A bit of paw swiping is perfectly normal and nothing you need be particularly worried about. If he's overly aggressive you might need to separate them. He's just making sure the kittens know he's in charge. It might be a good idea to separate him from the kittens, or at least make sure he has somewhere he can go to get away from the them.

When you say the kittens are allowed outside do you mean just in your yard? Or beyond there? You don't say how old they are, but it's not a good idea to let cats go outside until they're fully vaccinated and neutered.