I must be crazy!

I must be crazy.
I told you all that hubby gave me money for a trip to Sea World for Mother's Day.
Well, that trip is coming to fruition in three days.
Just Ava and me.
In the car.
For at least 4 hours.
I must be crazy.
We are staying with a good friend/sorority sister of mine from TCU, and hub is super busy this time of year and can't take off work, so this is jsut how it has to be.
So, before I talk myself out of traveling alone with her, I was wondering if you had any tips, advice, scripture, herbs, magic tricks, etc. to share???
Ava is a great kid.
But she has very little patience.
She gets antsy super fast.
And she doesn't sleep in the car unless she is wiped completely out.
I plan to leave just around nap time.
Is that a bad idea? I'm hoping that EVENTUALLY she will fall asleep.
And we have a DVD player in our car so that will work for about 35 minutes.
But what about the other two hours?

Here are my specific questions for all you mommies out there that have FAR MORE expertise than me.
-Is leaving at nap time a good or bad idea?
-What kind of fun things (games, toys, bag of things) are suitable for a new 2 year old? She isn't really into toys much, esp. in the car. That's the only problem.
-Should we take a few stops along the way to let her out and stretch/run/skip/whatever or just try to go as far as possible and only stop when necessary?
-Just how much benedryl can I give a 32 lb. 2 year old?

Just kidding about that last question...
I am excited about our weekend and we are so blessed to be able to do fun things for Ava such as this. And I know it will be much more difficult with more children, so I need to make the most of it and not sweat the small things. If only my type A personality worked like that!

Thanks in advance for your tips!!!