If you want to keep the sofas in same spot I would set the TV up in front of the Bay window and find a TV stand with storage for some of your children's toys/projects. That or place the Tv on the stair wall and set up the couches around that. I think the key is finding something that can store your childrens stuff so you can open up the room.

Picture of room with previous owners’ furniture/layout

https://www.houzz.com/magazine/how-to-get-your-furniture-arrangement-right-stsetivw-vs~18262852 Here's a good article. Notice how few of these rooms have furniture against walls. Learn to float!

My husband and I have done what you suggested by drawing up some plans We have started with the smaller version. Thank you for your offer of help. I think we are both realizing that we can’t get everything we dream of in the space as originally planned. He does not want to put a tv in front of a window because of the wiring etc. can be seen on the outside. He has mentioned also that with this size of room, it may be difficult to sit back far enough to view a TV. In terms of dining, since we seldom have a crowd for a sit down meal, I suggested that we not put a permenant dining table in. We can rent a table as the need arises and rearrange the room. If I can move my china cabinet to this space, it will open room in my 12x12 dining room so I can get a larger table in that room. If we use swivel chairs in the addition, we can easily turn the chairs for viewing or conversations. The posted picture is the latest version of our possible furniture layout. Floor lamps would go on each side of the sofa. The door to the left of the sofa will be a door size window so no traffic will go in and out here. The coffee table will be a padded bench with a tray. This plan may still be too tight We would love to see your thoughts with the original size space or the larger version.