Eating on the Run... Literally.

Folks, I need your help/advice. (especially runners) So, please stick around and read. It's time for some real talk. 

My half marathon is on Sunday. I'm mostly excited for it at this point because even though I know it's further than I've ever run, I've run some long distances and been fine (crazy crazy tired and numb-legged, but fine).

I know - for a fact - that I will need to be good an awake and warm by the time the race starts at 7am. I've also been told that I should eat something so I have energy. This is where I'm not sure what to do.  Usually, my stomach and I get along fine, but sometimes, especially on longer runs, it gets upset.

Does anyone have any tips/tricks so that I can eat in the morning and not having to worry about getting an upset stomach? I've read a few places about having a shot of espresso, my concern is that coffee is a diuretic, so how long before the run would I have to take it?

Also, any snacks/gels/chews/energy anythings you recommend for the run itself? I'm planning on having some recovery formula after I cross the finish line, but I am stumped as to what to do before/during.

So... thanks in advance (I hope)!