IMHO, making the checklist available is a nice courtesy.
In one previous position, we wrote up our checklists the day of the audit, so it wasn't possible to provide it at the time of the audit. However, I did announce the audits about 2 weeks in advance. In the e-mail, I let the dept and/or process owners know the basic things the audit was going to cover. This was well-received by the various managers. It gave them each a chance to look over instructions, postings and the like documentation to make sure it was OK. It also gave them a chance to give the other folks in the area a heads-up that the audit was coming.