Praslin surely has great beaches, but so do La Digue and Mahé, too. The outer islands have some cool (& expensive) places to stay as well.
Besides beaches, there are coral reefs for diving & snorkeling, inland forests with huge palm trees, small islands with birds and giant tortoises, etc.
not that much shopping or wild nightlife, really, but for that, there are other destinations to go to.
You can combine two or three islands for your visit if you want.
Check more attractions from for example here:
http://www.happytellus.com/seychellesPersonally, I loved the Seychelles.
Have a great trip!