Get some artificial plants or house plants and place them around. They sell glow in the dark stars which you can hang from the ceiling. Also, decorate with battery operated lanterns or you can buy lanterns and place battery operated candles in them or take a paper bag (cut out designs i.e. stars) and make your own luminaries and place battery operated tea lights in them. Also placing candles or battery operated candles around for a night effect For snack ideas what about smores. They sell indoor smore kits or you can use chaffing fuel and put a wire rack with a stand over it and make your own. Snacks: Popcorn, pretzels, mini hamburgers, hot chocolate, rice krispy treats. Sounds like a fun party.