I'd recommend taking fish oil for vitamin D, as it also contains proper Omega-3 acids (many things labeled with Omega-3 contain useless variants).

If you are going to be practical about it, taking a spoonful from a bottle each morning costs about 95% less than the equivalent dose from fish oil capsules.

Taking a swig of fish oil ("tran") in the morning is quite common in Norway. It is normal to start giving it to kids from when they are a few months old, to get them used to the taste.