Ibiza is a wonderful destination for families - short flight from Ireland and short transfers when there.
Santa Eulalia is lovely, also cala lleyna, cala llonga (really anywhere on the east of the island is very family orientated and relaxed). Es canar is a bit kitch with lots of amusements and trampolines etc, but it attracts a lot of young families, the beach is nice and safe, the hotels are a good standard and there are lots of restaurants.
Avoid Playa den Bossa and San Antonio.
Hope you have a lovely time ... thinking of going back again this year - especially now that the weather is so bad!!!