Depends. Can I wear a cup? Because 5 year-olds are at that dangerous and potentially-disabling height. (Or, as I keep having to tell my nephew, "It's a scrotum, not a speed-bag.") They might get me on the ground early and then overwhelm me.
I don't actually fight back - but I've certainly had the experience of being attacked by groups of 3 through 6 year olds, and let me tell you, them little rugrats can be dangerous. (Even moreso if you're a houseguest on a sofabed and the little bastards decide to jump up and down on you at six in the morning because mommy and daddy's door is closed and you're out in the open where they can get to you. )