If you want to have your wedding in a car you're going to need a lot of help. Cars are pretty small compared to weddings, so if you don't get help from everyone you know you won't be able to pull it off.
You can't just ask for help on the day of the wedding, either. You have to schedule (すけ) getting your friends' help ahead of time. They might have pretty tight schedules too, so make sure you plan early!