[The once and future king]

The obvious weapon of choice is the knuckle duster. One with spikes on etc. This will be useless in the hands of the infantile horde.

My real problem is bellieving that the kids would keep attacking me. Once I had picked out the toughest kid, lifted him over my head whilst bellowing in rage then piledriven the kid headfirst into the concrete I cant see the other 5yr olds doing anything other than breaking down in tears and wimpering.

The solution to this problem is obvious. We must have a time
machine. We can then trek through time looking for truely hard 5 years old, not the current crop of soft as shite western five year olds. I would stop of in Sparta.
Spartan 5 yr olds must the hardest 5yr olds in human history, but more importantly there entire culture would have socialised them into wanting to fight on and on and never surrender like wusses.

So in short this scenario is only realistic and feasible with access to a time machine.