How should I estimate quantites to print for race day?

We are having a first ever community 5K walk/race and are expecting approx. 1500 participants. The program has been strongly supported by the schools, including 6 elementaries.

I am going to have a booth and pass out free 3" stickers (that say I completed the race), little stickers they can use for tattoos and even smaller ones for fingernail decals. (all surrounded by info. about what I can do with the versacamm (I was primarily an embroiderer/screenprinter before)

Has anyone ever done any similar race events where they have handed out similar items? If there will be 1500 participants, how many of these hand outs should I have?

This is a first time for me and I've only had the versacamm for a few weeks, so I have no idea what to expect....any other ideas you have to promote my booth would be very welcome!

Thanks,
Kathryn