so many dietary restrictions

What about paleo pavlova? There are several recipes on line using honey instead of sugar for the meringue and whipped coconut cream for whipped cream.
If you want to do traditional cupcakes, It should also easy to find a paleo recipe. My secret for great vegan frosting is using equal parts of vegan butter or coconut oil to tofutti (vegan cream cheese.) The tofutti acts like a stabilizer.

Oh goodness! Maybe go Barefoot Contessa and create a make-your-own-ice-cream-sundae bar with sugar-free and dairy free ice cream as an option (http://sodeliciousdairyfree.com/products/coconut-milk-frozen-desserts/no-sugar-added-mint-chip). You could offer berries, bananas, nuts and then other toppings which meet only one requirement as additional toppings (e.g. crushed gluten-free cookies, fudge sauce, etc.... Make little signs to be sure that each ingredient is clearly labeled whether it is DF, SF or GF. And now each guest can indulge in a custom dessert. As BerryBaby says, "Good luck!"

This has come up previously and I have suggested asking those with restrictions for their ideas. They would know best. Best of luck!
BB💐