The only reason higher sheen trim was traditionally used was for durabilty and cleanabilty and protection from water. They have made vast improvements over the years in those departments. I think if you get a lower sheen just make sure its washable and scrubbable. Usually flat is on taller or textured ceilings if the ceilings are lower a higher gloss will help reflect light around. I personally like using a little sheen on wood and I also like oil better than latex on wood. It has a little more self leveling to it in my opinion so I would use an oil base eggshell or satin or low luster on the trim and a matte or flat latex on the walls and ceiling. Oil is harder to clean up and smellier and it takes longer to dry, but it is super durable.