My trip to Ibiza was interesting. My first mistake was the location of the hotel which was in Portinatx. While the entire island of Ibiza is beautiful, if you are looking to stay near all the action Portinatx is not the best location. It is about 45 minutes from the airport and Sant Antoni which is where most of the bars, clubs and day parties take place. And while the weather was pretty nice in August it did rain quite a bit while I was there which interfered with the planned water activities. I also recommend renting a car while in Ibiza ahead of time especially if you can only drive an automatic because the automatic vehicles were pretty much all rented.
I personally have always been a fan of all-inclusive hotels until I stayed at the one in Ibiza. The food was subpar, drinks were not that great and amenities were less than impressive. We wasted a lot of money due to staying at an all-inclusive because we spent so much time eating and drinking out.
Make sure you reserve all of your water activities when you get to Ibiza, there are several places to sign up for boat activities weather at the beach or at your hotel. We reserved a boat excursion online through Viator.com which was a big mistake. We tried calling several times to cancel our excursion due to the heavy rain and was told that we had to wait to see if we would be refunded. We had a very hard time connecting to the actual company as Viator.com is a third party and were not notified until one hour before the scheduled trip that it was canceled due to the weather. We also had to wait several days before our money was refunded.
If you plan to attend day parties I highly recommend booking in advance. While the day parties are fun, they get very crowed and the drinks can get expensive. Book a cabana or table to save some money and avoid the long bar lines. I also recommend going to Ibiza with a group of friends to split the cost as you will spend most of your money on drinks and clubbing if that is your thing.