I eat a lot of wild caught fish. But I love Barlean's Lignon Flax Oil. Barlean's is a great company and organic.
I would try this one because anything a kid will eat is probably going to be good.
www.barleans.com/omega-kids/kid-s-fish-oil-omega-swirl-lemonade-flavor-8oz-bke08flBut check out this one!! And it does come in pill form.
www.barleans.com/total-omega-oil-lemonade-flavor-16oz-bto16