There are literally thousands of posts on here with advice, reviews, party suggestions, etc. If you have specific questions (geographical areas, clubs, tickets, etc.) you can use the search function.
Also the main Ibiza-Spotlight site is chock full of useful info.
I'd recommend staying in Playa d'en Bossa. Check the Spotlight site for some hotel and apartment-hotel options.
It's hard to recommend party options not knowing what kind of music you're into.
I say rest up Saturday (Aug 20)... maybe spend the afternoon/evening dancing on the beach at Bora Bora then head into Ibiza Town for some food and drink.
Go to We Love @ Space on Sunday (Aug 21). It's an all day/night affair but you get one pass-out to take an evening break. There's 4 zones at various points during the day so you'll definitely find some music you're into.
Monday (Aug 22), my preference is Release Yourself w/ Roger Sanchez @ Pacha. He'll play an eclectic house set that keeps the crowd happy. Other options include the massive spectacle that is Manumission @ Privelege, and the harder sounds of Cocoon @ Amnesia.
Have fun!