It was easy to get off of the original question when the answers suggested that mixing is not a good choice. My experience has been that I have been the only one nude while my companions remained clothed. In every case I asked permission to strip.
I can only speak for myself but I would prefer to keep the peace among all. Thats always easier said than done. How about having two parties instead of one? A good friend of mine had a big wedding party at church to celebrate his 40th ( I think) and everyone enjoyed themselves. Before it got too late, he announced that my wife and I would be hosting a reception at our home for them and please come & enjoy yourselves. I think about half the original group of about 50+ showed up. Basically, the couples inner circle of friends. Could you set up the initial party as textile and the later one as nude? I think the attendees would self segregate and everyone enjoys the evening. I dont know if it would work for you but ours was a great time.
@Andy, my reading of your situation sounds like it will probably turn out just fine. My only slight concern would be if they decide to 'demonstrate', but if they are not too immature, they should be okay, especially if they're confident the textiles will leave first. :-D