Ive been to Ibiza 2 or 3 times a year for about the last 8 years (I used to DJ alot but now thankfully retired from all that). I still go and stay in San An, near the harbour at this awesome little family hotel (hostel is spanish – not to be confused with back packer type thing) it only has about 20 or so rooms, very modern, owners are very friendly. There are good connections to very nice beaches from the boats on the harbour (about 7 or 8 euro return). I recommend Cala Bassa / Cala Conte / Cala Tarida for beaches. Or if you are up for a bit of a walk head for Cala Salada which is very nice.
The hotel I stay at is called Es Mitjorn (http://www.esmitjorn.com/index.php?lang=en) It has a mixed bag of guests, usually DJs travelling in for a few days to small groups and couples, Never seen any kids there. The hotel staff are friendly, reasonalby priced, modern, clean and very quiet for its location!
If you need anymore tips be sure to ask!
Also as Wallop says try and visit formentera (ferrys from Ibiza town port). The beaches there are very very nice.