Pre-Race Panic Poop

It's been over a decade since I've done anything remotely competitive.  The last competitive event I was in was a swim meet in HS.  Before every swim meet I would poop 5 times and puke.  Then I would feel slightly better.  I've been anxious all week for the baby buggy 10K this Sunday.  I know, get over it already.  And yet I can't.  These are the things I am panicking about.

1. Not finishing
2. Finishing last
3. The B screaming through the race - fun to be had for all
4. Needing to poop at the race - ewwww portapotty
5. The B's breakfast - I'll have snacks but Breakfast falls right during the race
6. Getting to the race - parking lots close access at 6am, race doesn't start until 8:15.  I'm considering walking to the race start because it's only 2miles away.  But what if I get too tired to finish.  See item #1.
7. What I should wear for weather and what should I put the B in
8. Shins hurting
9. The B pooping during race.

As recommended by my sister, I'm going to make another list addressing the panic list by either;

1. How I can plan to prepare for that concern
2. Why that concern is either unfounded or extreme
3. What I can do to make myself feel better about that concern

So to address the concerns.

1. Not finishing -- This is probably extreme.  Worst case, I can walk to the finish.  Last year the slowest time was 1:54, which is something like a 16min split.  I can probably walk faster than that.
2. Finishing last --Why does this matter???  So what if I'm last?  Nobody has actually died of shame.  Try convincing my stomach of that.  STOP making me get the runs already?!
3. Screaming baby --I'm in the baby buggy race.  Other kids will be screaming too.  Note to self, don't forget headphones.
4. Poop --Can't think of anything for this, I'll just have to do it if the urge comes.  Or maybe it'll make me run faster?
5. B's bfast --I'll feed her before the race.  If she doesn't want to eat, then the snacks should fill her up?  And if she doesn't want the snacks, waiting an hour before eating is not coming close to starving her.
6. Getting to Race --I'm walking to the race location on Saturday to get the packet.  If that feels too tiring, I'll ask the husband to drop us off on Sunday.  I'll let him worry about the parking situation.  Maybe he can drive home and then walk back in time to see us finish.  He doesn't have to be at the start, it's not like I'm going to be much company.  Except the idea of going into a porta potty with the baby is not pleasant.  I'll have to poop a lot at home.
7. Clothes --layers?  I have a stroller, I can just stick outer layers in there.
8. Shin pain --They're just going to hurt.  Nothing I can do about that.  Ice after?
9. B's Poop --Waiting an hour to change her diaper won't kill her, right?

Any tips?  Or more things for me to worry about?