Lead by example. You won't convince a young mind to do anything it won't want to do unless they want to do it. Same goes for adults.
I would assume you didn't always follow the primal way of life either.
Let them be kids and do the usual kid stuff, when they mature they will follow their own path just like you did.
My 15 yer old crunches sugar cubes and drinks coke by the bucket full, so did I. But since my recent change to a healthier way of living iv never felt better and Im 48 this year.
I wouldn't worry about it too much.