While soffit and ridge does provide better flow, and therefore cooler attic space, you are fine to not add them. The cost would be so much more than you would ever recover and be economically wasteful. The only thing I would look at is an encapsulated batt on the attic access panel and possibly encapsulated batting around the bathroom fan ducts (hood duct if from the kitchen as well). Adding a power venting might be a good thing to look at, but the configuration of such really depends a lot on the attic, exposures, etc. to make sure you have good flow. In some cases, loose blown insulation can become displaced if you let too much wind blow through the attic.