Hi Jo-anne I would rather go to treamble valley than Hendra or Trevornick as I don't like sites that are all singing all dancing. When we first started going to campsites I would only go to ones like Hendra but have since found that I prefer ones that are quieter. My favourite site over that way is Silverbow Park at Goonhavern it is a beautiful landscaped park with rabbits literally everywhere! It has a swimming pool undercover and is just perfect.
The approach road is quite narrow but not to bad, I see you have a big caravan like us. I don't remember going in a tunnel
you head towards Newquay from A30 and turn off down what is known locally as the (big dipper) a massive down then up hill. Then you follow this road for a little way its windy but has passing places.
As for where to take the kids as you know I don't have any children myself but there is plenty to do in Newquay. Dairyland is nearby, there's Crantock beach, Minatura at Goonhavern.
Hope this is of some help.
Mandy