I also do not like or eat seafood of any kind.
So- what does fish have that you truly need to survive? Nothing.
However, it is rich in Omega 3 fatty acids which are very useful and healthy and have been linked to heart health.
Fortunately mother nature does not put all her Omega 3's in one place. Flax seed also is very rich in the Omega 3 & Omega 6 fatty acids. You can supplement your entire family with heart healthy Omegas via Flax Seed oils and meal.
On a related note, there are supplements that kids can take. I offer my my kids DHA/Omega chews that supplement their growing bodies with these fatty acids along with having them eat a balanced diet rich in vegetables, fruits and whole grains.
But there is nothing you cannot get from another natural source in fish and you can even get the fish derived fats in a supplement.
Good luck!