Maximize the current light by removing the console from the window. Make sure that the light coming through the windows is not blocked by objects in the sunroom/sunporch. Use brighter light bulbs. Keep windows and lightbulbs clean. Light colors and metallics will reflect light. Another ploy that is typically used in a bedroom is to place a mirror behind a lamp on a nightstand, but the same can be done behind an end table. Beyond that, an electrician can assess/advise what it would take to install additional lighting. As far as the room layout, it is very challenging, as you’ve noted. Have to ask…what is the stained wood section with the shelving? In the hallway(?) next to it, the door on the left would seem to open to the wall there. Is that area a hallway? Is it necessary? It would be nice if that whole awkward area could be taken out. If all that has to stay, I’d consider making a closet or a built-in shelving unit for all of the children’s toys/gear. One last question…the new couches…are they a couch and loveseat or 2 full size couches. A detailed to-scale floor plan with measurements and furniture sizes would help us determine a better furniture layout.

A soft color on the walls actually is brighter than plain white. A white or off-white carpet works really well and will bring the dramatic ceiling to life.

Brighter artwork and place the mirror where it can reflect light.

No more ceiling lights, use table lamps and floor lamps for a more softer light.

Here is my concept render with a very nice Benjamin Moore Healing Aloe:

https://www.benjaminmoore.com/en-us/paint-colors/color/1562/healing-aloe

It looks like you get good natural light from the open front door. Consider a door with some glass to take advantage of that and a mirror over the fireplace to reflect that light.

IDK budget but.

I would get a much larger rug