Share prize money from conference presentation award with co-authors?
I think that it is important to recognize that the biggest value of the award is its contribution to your C.V. and future career, not the prize money.  As such, I think you should approach the question of the money as generously as possible: after all, you gave a good talk, but many of the aspects of that good talk depended critically on the contributions of your co-authors.

What, then, is a fair way of allocating the money?  Pretty much any numerical formula that you follow will both a) leave some people feeling that their allocation is too big or too small and also b) only be a few dollars anyway, given the number of people involved.  

I would therefore recommend defusing the question entirely and turning the prize money into an investment into future goodwill and papers: suggest that it be spent on going out for a fancy dinner together (or similar such outing) to celebrate the success of the collaboration!