That's great to hear your son wants to help out! The first step is for him to decide on something he loves and wants to protect. From there he can choose from lots of ways to help- remembering that passion and well-informed word of mouth are extremely powerful. For example, even without giving a penny if he wants to protect the oceans a great way to do this is by eating sustainable fisheries products. If he tells others about Seafood Watch then he could help lots of people avoid choices and purchases that harm the environment.
http://www.montereybayaquarium.org/cr/seafoodwatch.aspx
If your family wants to fundraise, then there are lots of ways to do this (but again homework and speaking about it to spread the word help - IF that's something he wants to do). In one of the places I've worked kids used to paint and sell postcards, and the proceeds went to a village education project. What to support should be in line with what he loves- in general lots of projects needing funding (at all scales) can be found online. In searching these, it helps to see groups that tell you what projects or actions they are involved with and how the money will be used- as well as examples of successful past projects. If you're not finding the information you need to make a decision about whether or not you are interested in their group, then don't hesitate to contact someone from the group to ask questions. Or if you're son isn't able to find the right NGO/non-profit he likes, then consider finding out which professors or grad students may be doing fieldwork to understand those animals- supporting student project is a great way to learn a lot about the oceans with little money. But if you want direct protection and conservation action, then look into a non-profit or NGO.
I don't know of any squid conservation foundations- some populations are protected through fisheries legislation. It would be worth looking into the latest on who's spearheading the work to conserve the Sepia apama in southern Australia. For marine mammals- this group
Donate to Save Whales and Dolphins | Whale and Dolphin Conservation seems to have a good variety of ways to help out whale conservation, at many different levels of giving (though I don't know the group myself). The NGO that I work for, Conservation International, has a good website for finding more information about marine conservation (I especially like the everyday solutions in the "discover our solutions" tab).
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If you are interested in protecting coral- we work to protect the global center of coral (and reef fish) biodiversity. One of our sites, the amazing Ayau Atoll, is working hard to stop compressor/cyanide fishing for the aquarium and life reef fish trades (which kills coral and lots of other animals):
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No matter what your son wants to support- this is wonderful that he's interested in helping out- and his most effective means of doing so is to spread the word and inform others!