Preparing a child for a first sleepover when both child and parent are nervous

My child has been invited to a first sleepover and is excited in daylight, worried at bedtime. To be honest, I'm a little nervous too. We've met the other parents and checked the arrangements. I want to give my child a way to call home if needed without framing the night as something dangerous. Did you make a simple pickup plan in advance, or does emphasizing an escape route make the anxiety worse?