I am trying to help plan a week in Spain for some of our wedding guests after they spend their first week in Madrid for our wedding (in July). They said they would like to visit Barcelona and also spend a few days on the beach. A week is not very long so I was wondering if there are any recommendations for a place (or places) they can go? Any other suggestions of possible places to go/see aside from this plan would be greatly appreciated!

Definitely Sitges.
Good beaches.
Plenty of nightlife,restaurants.
Easy access form Barcelona.