Most Indian desserts are milk based, but you can substitute it with almond milk. My GM refused to have milk from the milkman whose hygeine standards she was not sure of. So she used to make milk with almonds or melon seeds by grinding them in water and the boiling the mix. She made all sorts of milk pudding in the milk.
Vegan Indian desserts off the top of my head could be one of these;
Rice pudding or a ground rice pudding (phirni) cooked in almond/melon seed milk. You can buy packs of such seeds at most decent Indian grocers.
Boondi in syrup
Carrot halva using almond milk
Or simply make a nice fruit salad. It is very welcome after a rich Indian meal. Most of our friends prefer it to very sweet sweets these days.
Have a great party. I would love to see a few photos of your food :). You can post them on https://www.facebook.com/mamtaskitchen/