Hiya, I thought i would just give you a little friendly advice!!!
I love ibiza, i worked in Portinatx, Santa Eulalia, Sargammassa, Playa den Bossa and Es Cana!
Seriously as a rep i have to know the island back to front to advise holidaymakers everyday to make the most out of their holiday!!!
Playa den Bossa - Excellent choice, home to the waterpark, activity park and also for entertainment of an evening you have your hotel and also the wide range of bars and restaurants!!!! Only 15 mins away from airport so no long travelling for the little one! Only 5-10 mins bus ride into Ibiza town!!!!
Es Cana - Maybe, depending on your needs as a parent for your children this could either be a holiday of a lifetime if you prefer to stay in the hotel for entertainment! (Ereso Hotel- look at reviews) However, one down point, one of the beaches has a slight undercurrent which is always flagged however is unpredictable as to where it goes so depending on how far out in the sea you go the more dangerous!!!! With children a definite NO NO for me!!! (Personal opinion)
Portinatx - I worked here the longest so i could probably give you so much information on this resort!!!! Hotel Presidente - spectacular 4t (Thomson Superfamily) accomodation, full time entertainment for both children and adults!!! You have the creche for the 2yr old (if turns three before holiday can choose between the creche and the kids club) Kids club for the 5 yr old and relaxation for yourselves!!!! Set in a cove, portinatx is a fairly small resort, however it has 3 beaches and 2 of which are golden sand! There is also another beach Cala Sara, however this is a good hour walk! there are a few restaurants and a couple of bars, one of which delboys is a english bar with your normal kareoke and quiz nights, but you will love the enetertainment up at the hotel! Wide excurs with thomson and also there are local buses which take you to ibiza town at a cost of about 2.50e per adult!!! Bargain!!!!
I hope this might have give you a little more information and if you do have any questions which i may be able to help you with, let me know!!!!
vicky x