I think I have lost my mind

I decided very last minute to sign up and run another 5K, this Wednesday night! Normally, ok no big deal.  We are in the high 90's all week. Wow, this might be tough. In addition, the husband is working an over night shift and my babysitter has to leave by 9.  Yup, I will run like the wind (back to the car).

I have the running bug so bad, but I do off set it with my weight training days and still give myself two days off a week.  Knowing all of this I am struggling. I really want to be a part of the Medtronic race, but I think it might have to be a 5K.  I am signed up for a 10K and 10 miler in September but the thought of racing those already scares me.  I know I can do the 10K but being in the throng of people I always tend to move a little faster, and fatigue a little faster.

Any suggestions? Just do the 10K and be proud of myself or stick with the safe bet of the 5K? The weather is also so unpredictable! It has been freezing some years and a heat wave other years.