[imaohw]

I haven't read every single post, so somebody else may have submitted this solution, but if not, I humbly present it here:

I propose that a healthy adult (or relatively healthy--one who has gone through puberty and has no functional physical defects) can pummel five year olds until he gets tired, and considering that one could probably incapacitate a five-year-old with a single hit, I believe this number would be much higher than thirty for most.

There are several points to be taken into account:
1) In response to whoever commented on getting bitten in the balls: the situation clearly states that you will be wearing a cup
2) While the five year olds are "swarming" around you and not lining up one one one, as a previous poster noted, only a certain number can reach you at a time. If we estimate this at eight (which I think is fairly generous, considering their diminutive reach), then it should be obvious that no adult would really ever be threatened, at least until fatigue strikes. I think that four or five rounds of head bashing would be quite easy for any adult.
3) While it is true that they can bite, these would not really incapacitate an adult; they would annoy, and maybe sting, but not actually limit one's ability to fight, Unless perhaps they bite off a finger, but one's hands should be moving quick enough to prevent that.
4) As the fight progresses, the adult will probably have a ring of bodies around him. Any remaining five year olds will be forced to trudge through these bodies to reach the adult, and will probably get tripped up along the way, making them increasingly ineffective as the fight goes longer.
5) As a post near the top stated, you can grap one by the feet and swing him around. You'll be able to slap the crap out of any five year old before he gets within five of his arm-lengths of you.