The kids world in alicante is very good especially on weekends when locals attend, as gemstone says the ride costs can quickly mount, lovely carousel at the far end. The karting also great day out if combined with beach visit and icecreams. Do check the life resort because unless rules have changed children arent allowed in the pool. Guardamar also has a very good fair and quite reasonable cost located down by the park, need to check whether its open in feb as most things for kids dont start till easter time. Dont forget the many free parks scattered around ga and further afield.
Weve also visited mundomar numerous times really good day out, terra mitica is also good but they might not be big enough for some rides. Back near elche is the safari park i dont like it lots of sad animals but seems popular