We use our formal living room as a study/library. There's a nice desk in there, 5 bookcases, and 2 chairs. I think it looks nice and it is useful to us. We use that room every day.

The dining room can't be fully seen from the front door, so it's more casual and less decorated. I have a child's school desk in there (an old one that has the chair attached), small bookcases with games (wish I could afford to replace that set up with a closed storage unit of some kind) computer, and the wooden kitchen set that my dad made for the kids.

When my first two children were young I actually did convert my formal DR to a playroom. I was so tired of their toys cluttering up our family room and they still wanted to be close by where I was instead of off in their room playing with their toys. It opened up to the front door and yes, it was what people saw when they can to visit; but most of our friends had children also and I think everyone appreciated the kids having their own place to play free of any furniture, but still close by. We took out the chandelier which we never liked anyway and put in a semi-flush fixture so that you could walk underneath. I owned a drop leaf table and about once/year I'd move all the toys to the garage and set up for a formal dinner. If I had wanted to make it more private I could've installed french doors leading from the entryway and covered the glass with an opaque film or fabric, but I always saw this as a temporary thing while my kids were young. As they got older, they were OK having their toys in their rooms and I set up their closets with closet shelving and organizers to store their toys in plastic bins.

A few months ago someone posted an amazing picture of a built-in that covered an entire wall and had doors, behind which were shelves with toy bins and games. All the toys were stored away and not visable, but fully accessable.

Are the bookshelves in your LR built-in? Perhaps you could convert it to something similar.