Actually, chocolate chips aren't a really good choice for something that you need to be fairly firm once it cools. They're not good for coating, nor for making chocolate cups or molds. CChips are formulated so that once, melted, they never really get that firm again. They're made to go into cookies and are supposed to be soft after they've been baked.
You'll have much better success, and won't need to add anything extra--if you buy coating chocolate. You can buy candy melts at WallMart or craft stores. You'll probably find Wilton brand melts there--not the best chocolate, but it should work for your needs. If you have a candy supply/cake decorating store in your area, you may be able to find Merckens--much better quality chocolate. Even some restaurant supply stores carry Merckens brand chocolate. When dipping or making molds, I like to melt the Merckens dark melts, and then stir in a tablespoon or 2 of baking cocoa for a richer flavor (takes a bit of stirring to get it to work in, but you can).
How are you making your cups? I love doingn the ones where you blow up a balloon and dip it. So easy, and they look so cute. You can, with a little practice, make the cups look like petals.
Edited to add--meant to mention. If you absolutely MUST use chocolate chips, baking chocolate, or a regular candy bar for your cups, add a small square--about 1" of parafin to your chocolate. Let both melt completely,and stir until well-blended. The parafin will give your chocolate the firmness and gloss you will want for your cups to look as good as possible and to hold up to whatever use you plan for them.