well i live in prague so im always glad to help if you have questions
opera is great, like faust said. the narodni divadlo and obecni dum are both
gorgeous. as far as shopping is concerned, there isn't too much to check out, and i don't know what shops you prefer...but at Vaclavske Na Mesti they have a few good shops, a huge zara, a huge mango, a great shop called Vero Moda..
there is also a shopping center in Novy Smichov and another one in Metropole, although it is quite far from the center of Prague.
if you like animals, you have to check out the Prague zoo. it's gorgeous.
you should also visit (obviously) Prazhskij Hrad, which is probably one of the biggest tourist attractions, along with the Charles Bridge.
another lovely place is Petrin Hill, you can take the (foonikuler..<- thats in russian, no idea how to say it in english..) up there and they have a mini rip off of the Eiffel Tower and lovely gardens.
have fun!