Well I haven't been to any of them but I'll try and help!
Firstly I think that Sunnyside has closed down - not 100% sure about that but if you have a search around forum I think it says somewhere..
I also think that Rosecliston only takes bookings for 4 days minimum so if you were only wanting to go for a weekend you would have to pay for longer I think.
I've also just had a look at the camping tariff for Smugglers (
Link) and it is showing £0.00 for all the prices from now until 21 June. I'm not sure if this means they are all booked up but I guess you could find out by calling.
Another campsite that you haven't mentioned is:
Tregustick - (
Link)
If you do end up going to Tregustick, let me know how it is.. I'm thinking of going this summer
