Any party is better with karaoke! This is actually better when people aren't drinking, because you don't get one person who can't sing even when sober hogging it all night.
On the drinks side, mocktails.
A mocktail is a non-alcoholic cocktails, thus the reason for calling them mocktails. Martinelli's sparkling apple cider is an appropriate substitute for champagne, which is good to drink when celebrating something.
I once made my younger cousin a virgin Moscow Mule with just ginger beer, mint, lime and ginger slices.
Spiders are also great, it's basically a glass of soft drink, usually creaming soda, with a scoop of vanilla icecream. Although depending on where you are it might be a bit cold for that soon.
We had a dinner party for one of my friends a few years ago. Some of the drinks were non-alcoholic cocktails and punch. It turned out really well and people talked about it for months after. There is much to say about nice restaurant that has both cocktails & mocktails, it is great fun! Especially if it has a cozy atmosphere. You can just snack & chat & drink whatever you want. There's also cosmic/late night bowling. Amusement park night. Nice dinner at home. Cooking class. Go out to a fancier movie house. I guess it all depends on where you live.