Hi Chatelle and welcome!
I'm not really sure if the brownie mix will work in chocolate molds, but I'm guessing not. It would be pretty easy to just make them like regular brownies and then top with Easter colored icing and candies. There are plenty of dairy free icing recipes (search for vegan recipes) or, if you have a recipe you like, we should be able to suggest substitutes for you. If you can find safe chocolate chips, those will work for melting into molds or they can be sprinkled on top of the hot brownies and then gently spread once they melt.
Also, FWIW, the popping candy (Pop Rocks) we have here in the US contains dairy.
I'm going to move your post to the recipes thread so hopefully more people will see it and respond since it's been a long time since I've cooked dairy free.