Documents and the border
Montenegro is outside Schengen, so you pass a full border control. EU travellers use an ID card or passport, everyone else a passport; check the visa rules for your nationality before you travel.
Every passenger must be present with their document; children need their own as well. The vehicle and chauffeur carry all paperwork required for the crossing.
When it is busy and how to avoid it
In summer, between 9am and noon, queues at the crossing can add 30 to 90 minutes. Leaving before 8am usually avoids the wait and leaves the cooler part of the day for walking around Kotor.
What fits into one day
A typical day covers Perast with the view of Our Lady of the Rocks, the old town of Kotor, and a viewpoint above the bay on the way back. With an early start Budva fits too.
Your chauffeur stays with you for the whole day; entrance tickets and guided tours are not included in the driving price.