I am fairly confident they won't allow a caravan and a large tent on the same pitch, however if you are happy to pay for two grass pitches (not hardstandings) they may be able to accommodate you on adjoining pitches. You need to ask the site directly.
I did this at one site we went to with our old Van (2 berth + 4 man tent)
They wernt very keen on the idea really but agree'd in the end. Their concern was for fire safety, but i couldnt see how its much different to an awning.
Its really up to the site if they will allow it though, ask, but dont hold your breath.