WestWind Drive-in's are great! It's a relaxing and economical way to see a movie with the kids.
It's cheap! The entrance fee for adult is under $8. The fee for kids under 11 is less than $2. But wait, there's more! If you come for the first movie, you can stay for the second one, on the same "ticket." The second movie of course will start later in the evening. If you're OK with the time, and the kids aren't falling asleep, then you get two movies for the price of one.
An idea would be to pick up a pizza and some drinks before driving in.
If the kids want popcorn, buy a large bucket. They usually give you one free refill with a large.
The parking lot consists of a lot of "hills." When you drive in, you need to decide if you want to point the back of your car towards the screen or the front. You'll be parking on a side of a "hill." So your car will be pointed up or down. It won't be flat.
If you're planning on sitting outside on lawn chairs or your tailgate, back into your spot. Make sure you can shut off all the lights in your car when the tailgate is open. That will prevent you from bothering others around you. The workers at the theater will come driving around from time to time too to tell you to shut off your lights if they're on.
After you pay your entrance fee, your receipt will have the radio station number on it. You'll have to tune your car radio into that station in order to hear the movie.
If it's a warm night, with not a lot of wind, you might think about sitting outside with a battery powered radio. Or, if you can shut off all the lights in your car and still have the radio on, turn up your car radio a bit.
To get a little better sound experience, drive around the parking lot a bit and find the pickup truck with the extra speakers resting on top of the cab. Park close to that guy, preferably in front.
Last Bit of Advice
If you're running late, try tuning your radio to (96.7) when you get into the area. That's usually the family movie station. You'll be able to hear the movie, and maybe see it while you're waiting in line to pay.