Ok, for those who don't know me...
MY PREVIOUS POST WAS MEANT TO BE HUMOUR
Although it is factual, the NT manager on site did check with Stephen before saying yes to STACK.
I would suggest it would only be courtesy to let them know you are planning a gathering, no matter how informal, if there will be a lot of you going. If nothing else it gives them a chance to promote it, they are VERY supportive of kite activities.