Propensity for Intensity or 10 mile or 5k race?

Based on the results of last years Capital Pursuit race, I am torn between whether or not to sign up for the 10 mile or the 5k which is 3.1 miles.
I would possibly come in last if I ran the 10 mile.(part of me says "so what do it anyways").
I certainly would  finish but I don't know that I could do it in less than 12 minute miles and thats the cut off time for police escort on the streets("thats motivation enough to run faster").
I have only been barefoot running since June so I have not developed the speed yet("what if I look like a total looser").
I am thinking too though that I am underestimating myself ("tends to be the case"). It would be a race after all and the excitement of that goes pretty far.
That being said I could go much faster and be at least a middle-of-the-packer and maybe better if I ran the 5k ("tempting and would boost my spirits for the half").

I am already nervous to have the attention that running barefoot will bring but I do want to do well ("I know they are going to ask me questions").
 I am running the Des Moines half marathon on October 18th ("yay!") so I do have a distance race coming up.
I want to be realistic in what I am ready for but at the same time my propensity for intensity tells me to go all out and do the 10 mile ("wooohoo run baby run!!").
I will decide by Sunday at the latest. One week before the race! (how mature of me!)