So Cara, I can't your house out of my head so I thought I would put a design board together for you.
This is what I was thinking for the entry. Same colors on the walls as the Family room. French doors on the music room like you had talked about. A jute rug trimmed with black or brown. Large round table(not in this finish. Maybe black or even one with a table cloth) placed where your current one is. A few baskets placed on the floor next to the table to add texture and added storage. This table would really be great with knick knacks and the tall flowers you had mentioned. A cute little bench next to the door(again black would look nice) with a system of hooks for guest as well as a cute old looking sign of some sort hanging above. More frames for the wall on the left as you are exiting the entry and entering the hall and family room(I think there was wall space there).
Click on the design board arrow to view the family room design board.
I think a nice neutral color on the walls will look great with all of the vertical space and natural light. This color(it's the greenish brownish blob above the one chair), or one similar, will allow you to add and change color with accents throughout the year. The wall unit shown is similar to the pottery barn one you showed me today. I like the shutters on this one. The wall sign above it says, "Delighted you are here." I know you talked about doing a leather sectional but I couldn't find an image of one so lets pretend that this one has the right lines and is a sectional. I like these slip covered chairs. Pairing them with ottomans and placing them on either side of the fire place would look great. Using bamboo blinds on the two windows will add warmth and texture as well as tie into the dark brown of the sofa. The black cabinet would look great on the one short wall we were talking about. You could do a picture collage above the cabinet of all your cute babies and sweet family. I found this image of a wicker coffee table which I thought was fun. I still think something square or round would work great in the room too. This tree would look nice next to the wall unit on the big wall. Next to the tree on the half wall(near the hallway to your bedroom but still in family room) a small black bookcase with baskets and floor pillows(which I couldn't find a good image of) would be cute for a kids corner.
I used a blue color scheme but with your neutral large pieces you could use just about any color you would want. The only problem with doing the design boards is that you are limited on the images you can upload. So, the images in you board are just ideas of what we had talked about. I am sure you could find similar pieces at other stores for better prices and the right lines you are looking for.