The following campsites are within a 30 minute drive, so are useful for your first/last night:
Fortrose Bay Campsite - good for seeing dolphins
Rosemarkie Campsite - good for seeing dolphins
Note: Rover Rentals is a member of the Camping & Caravan club, so you get members' rates.
Places to empty the toilet cassette, without staying the night:
Highland Campervans - 5 miles away. £5 charge
Ardtower campsite: - 1 mile away. £10 charge