This not a good decision in the slightest, and not better for the animals, or the aquarium.
The animals will not have a better life at Seaworld, Helen and Chester are socially well bonded, have excellent relationships with their trainers, and are both non releasable non breeding animals. There are no other Pseudorca in continental North America, so the two would be separated, with Helen most likely going to San Antonio and Chester to San Diego. While both would likely do fine and adapt well to the moves, there is no genuine benefit to it. The pools they would be going into at Seaworld are smaller than what they live in now, and although Helen would have more dolphins of the same species to interact with, Chester would likely never be housed with many animals. Chest would go to the dolphin show stadium most likely, where her social grouping would consist of two pilot whales. SW does not mix species as none of their show dolphins (all female) are on contraception and they do not wish to risk hybrids. So social situation, especially for Chester, would be of limited benefit.
As for Daisy, the porpoise, the only other small cetaceans in North America are the Commerson's Dolphins at Aquatica, where she would not go. Most likely, she would be transferred to San Diego as well, where she would likely be housed either by herself off display or with their belugas, which would make her the only animal to have a genuine increase in social interaction, assuming their beluga group accepts her.
As for your other pondering, the decisions does indeed spell instant death for any non releasable cetaceans. While their marine mammals rescue program will still operate (it is independent of the aquarium), now any cetaceans that strand in the future and are deemed unreleasable will have to be euthanized, unless further agreements can be worked out.
