To Kiss or Not to Kiss

So my oldest son has reached that age where he hates to hug and kiss people. So over a weekend where we visit relatives he doesn't want to great anyone at all or say goodbye since he will be subjected to hugs and kisses repeatedly. My younger son has no problem as of yet and will kiss anyone. So my instinct is to say that he doesn't have to kiss anyone he doesn't want to. Is this incredibly rude? So to kiss or not to kiss, that is the question.