Six Flags Marine World has a terrible record of abuse and neglect of the animals housed there. If you don't really care about the message sent to your children that it is okay to abuse animals for our entertainment then, have a great time. If, on the other hand, you don not approve of the mistreatment of animals for profit, then take your kids elsewhere. The Oakland Zoo actually has a reputation for being one of the most progressive Zoos in the country, with a reputation and proven track record for truly taking good care of their animals.
Elephants seem to have gotten the worst of it at Six Flags. Six have died there in the last decade from abuse and neglect of injuries and medical problems. One elephant suffered from a huge, untreated tusk abscess for some time while still being forced to perform and give rides. Imagine yourself going to work everyday with a terrible tooth ache and gum abscess while your boss comes around through out the day hitting you behind the ear with a sharp spike because you aren't working fast enough for him. Not fun.