Around Port Macquarie - just before you get to Port Macquarie you can camp at a place called Diamond Head, that's in Crowdy Bay National Park and it is a great campsite, but very popular at that time of year and so you may need to book ahead. Beautiful spot though and good facilities. It's about 35-40 mins south of Port Macquarie. Search NSW National Parks website. Alternatively the other side of Port Macquarie, about another hour north of Port Macquarie is Hat Head National Park and it has a couple of different campsites as well as caravan parks (in Hat Head township or a great location caravan park at South West Rocks under the goal). Really stunning coastline (see a couple of our blog posts for pics here:
http://awildland.blogspot.com.au/search ... nal%20Park).
Around Byron Bay there are caravan parks but for national park beachside camping you would have to stop near Broadwater or Evans Head, which is about 45 minutes south of Byron Bay, and that is in Broadwater National Park or neighbouring Bundjalung National Park.
Around Coffs Harbour there are a few options here. North of Coffs Harbour is a small town called Red Rock, about 45 mins north, which has a nice caravan park behind the beach. From Red Rock south to Coffs Harbour there is also Station Creek which is a beachside, limited facilities camping area in Yuragyir National Park and popular with local surfers. Also just 15km south of Coffs Harbour the small town of Sawtell has a great caravan park behind the beach and beside Bongil Bongil National Park. Very nice little town too with great cafes and shops.
hope this helps.